Lithographic printing plate precursor

ABSTRACT

A lithographic printing plate precursor is disclosed, comprising a hydrophilic support having thereon a heat-sensitive layer containing either a microcapsule containing a compound having a functional group capable of reacting by heat or a fine particulate polymer, wherein (1) when the heat-sensitive layer contains a fine particulate polymer, the fine particulate polymer may be a fine particulate polymer capable of combining or incapable of combining by heat used for the image formation and the fine particulate polymer has a functional group capable of reacting with a functional group present in another fine particulate polymer or with a functional group present in another component in the heat-sensitive layer; or (2) when the heat-sensitive layer contains a microcapsule containing a compound having a functional group capable of reacting by heat, the microcapsule may be a microcapsule having an outer wall capable of rupturing or incapable of rupturing by heat used for the image formation and a light-to-heat converting material is contained in the heat-sensitive layer or in a layer adjacent thereto.

FIELD OF THE INVENTION

[0001] The present invention relates to a negative lithographic printingplate precursor comprising a support having a hydrophilic surface, and ahydrophilic image-forming layer. More specifically, the presentinvention relates to a lithographic printing plate precursor capable ofplate-making by scan exposure based on digital signals, ensuring highsensitivity and long press life, and providing a printed matter free ofresidual color and staining.

BACKGROUND OF THE INVENTION

[0002] In general, the lithographic printing plate comprises anink-receptive image area for receiving ink during the printing processand a hydrophilic non-image area for receiving a fountain solution. Asthe lithographic printing plate precursor for use in the manufacture ofsuch a lithographic printing plate, a PS plate comprising a hydrophilicsupport having provided thereon an ink-receptive photosensitive resinlayer (ink-receptive layer) has heretofore been widely used. Formanufacturing a lithographic printing plate, the lithographic printingplate precursor is usually subjected to mask exposure through a lithfilm and then the non-image area is dissolved and removed with adeveloper to obtain a desired printing plate.

[0003] In recent years, digitization technology of electronicallyprocessing, storing and outputting image information using a computerhas been widely popularized. To cope with this digitization technology,various new systems for outputting an image have been proposed and areactually used. To keep up with this tendency, demands are increasing fora computer-to-plate (CTP) technique where a printing plate is directlyproduced by scanning an active radiation having high directivity, suchas laser light, according to digitized image information withoutintervention of a lith film. Thus, it is an important technical problemto obtain a printing plate precursor suitable therefor.

[0004] In the plate-making process of conventional PS plates, the stepof dissolving and removing the non-image area after the exposure isindispensable. This additional wet processing as an indispensable stepis another problem demanded to overcome in conventional techniques.Particularly in recent years, a great concern in industry as a whole isto give careful consideration to global environment. From both of theenvironmental aspect and the process rationalization aspect to keep upwith the digitization, demands for a simple processing, a dry processingor no processing are more keenly increasing.

[0005] From this standpoint, the following method has been proposed fordispensing with the above-described processing step in conventionaltechniques. That is, the method is a plate-making system where aphotosensitive layer capable of allowing the non-image area of theprinting plate precursor to be removed during the usual printing processis used and the plate after the exposure is developed on a printingmachine to obtain a final printing plate without passing through adevelopment step. To speak more specifically, for example, a method ofusing a photosensitive layer soluble in a fountain solution or an inksolvent and dynamically removing the non-image area by the contact withthe impression cylinder or blanket cylinder in the printing machine isknown. However, if a conventional PS plate is applied to this printingplate in the on-press development system, the printing plate precursormust be stored under completely light-shielding and/or constanttemperature conditions until it is mounted on a printing machine becausethe photosensitive layer is not fixed after the exposure.

[0006] In recent years, some solid lasers having high output becomeavailable at a low cost, such as semiconductor laser and YAG laser. Withthis progress, a method of using such a laser is expected as highlypromising means for solving the above-described technical problem. Inthe high power density exposure system using these high output solidlasers, various phenomena different from the photoreaction occurring inconventional photosensitive material systems for low to medium powerdensity exposure can be used. That is, various structural changes suchas chemical change, phase change and morphology change can be used. Therecording system by this high power density exposure is usually called“heat-mode recording”. This is because in the high power densityexposure system, the light energy absorbed by the photosensitivematerial is converted into heat in many cases and the heat generated isbelieved to bring about a desired phenomenon.

[0007] This heat-mode recording system is greatly advantageous in thatfixing of an image after the exposure is not an essential matter.

[0008] More specifically, the phenomena used for the recording of animage on a heat-mode photosensitive material do not substantially occurin the exposure to light having an ordinary intensity or at an ordinaryambient temperature, therefore, fixing of an image after the exposure isnot necessary. By virtue of this, for example, a system may beestablished, where a photosensitive layer capable of being insolubilizedor solubilized by the heat-mode exposure is used and even when the layerafter the imagewise exposure is exposed to the environmental light foran arbitrary time period and then developed (removal of non-image area ), the image obtained can be free of any change.

[0009] By using this heat-mode recording, a lithographic printing plateprecursor suitable for the above-described on-press development systemmay be obtained.

[0010] As one preferred example of the method for manufacturing alithographic printing plate according to the heat-mode recording, amethod of providing a hydrophilic image-forming layer on a hydrophilicsupport, imagewise exposing it by heat-mode exposure to cause changes inthe solubility and dispersibility of the hydrophilic layer and ifdesired, removing the unexposed area by wet development has beenproposed.

[0011] Conventional printing plate precursors using the heat-mode systemhave, however, a serious problem, that is, the non-image area is poor inthe resistance against staining or the image area is low in thestrength. In other words, improvements are necessary in the point thatthe change in solubility of the image-forming layer upon exposure issmall near the support as compared with the change near the surface ofthe image-forming layer. In the printing plate precursor using theheat-mode system, generation of heat at the heat-mode exposure isattributable to light absorption by a light absorbent in the recordinglayer. Accordingly, the quantity of heat generated is large on thesurface of recording layer and small near the support. Therefore, thedegree of change in solubility of the recording layer is relatively lownear the support, as a result, the ink-receptive layer in the exposedarea which must provide a hydrophobic ink-receptive layer is sometimesremoved during the development and/or printing process. If theink-receptive layer in the image area of a negative printing plateprecursor is removed, the printing performance encounters a problem ofshort press life. In particular, when a metal support having highthermal conductivity preferred in view of suitability for printing, suchas Al, is used, the temperature near the support is much more preventedfrom increasing due to the thermal diffusion and the above-describedproblem comes out more seriously. For obtaining a sufficiently largechange in solubility near the substrate, an extremely large exposureenergy is necessary or an after-treatment such as heating must beperformed after the exposure.

[0012] For example, Japanese Patent 2938397 describes a method ofheat-fusing thermoplastic hydrophobic polymer fine particles by infraredlaser exposure to form an image, fixing the plate on a cylinder of aprinting machine and performing on-press development with fountainsolution and/or ink. This method of forming an image by mere heat fusionensures good on-press developability, however, when a heat-sensitivelayer is provided directly on an aluminum substrate, the heat generatedis deprived of by the aluminum substrate and a reaction does not takeplace on the interface between the substrate and the heat-sensitivelayer, while gives rise to an insufficient press life.

[0013] Similarly, JP-A-9-127683 (the term “JP-A” as used herein means an“unexamined published Japanese patent application”) and W099/10186describe a technique of heat-fusing thermoplastic fine particles andforming an image by the on-press development, however, the press life isalso insufficient.

[0014] JP-A-8-48020 describes a method of providing an ink-receptiveheat-sensitive layer on a porous hydrophilic support, exposing aninfrared laser and attaining the fixing to a substrate by heat. However,with the ink-receptive coating, the on-press developability is bad anddebris of the ink-receptive heat-sensitive layer adhere to the inkroller or printed matter.

[0015] JP-A-10-287062 describes a technique of providing anink-receptive heat-sensitive layer on a hydrophilic swelling layer andin this case, absorption of heat by the aluminum substrate may beprevented, however, if ink is attached before the hydrophilic swellinglayer is swelled by fountain solution, the ink poorly spreads and losspaper increases.

SUMMARY OF THE INVENTION

[0016] As described above, a heat-sensitive material favored with goodon-press developability, high sensitivity and high press life has notyet been obtained. Accordingly, the object of the present invention isto provide a lithographic printing- plate precursor capable of on-pressdevelopment of forming an image by heat, which can exhibit good on-pressdevelopability and ensure printing of a large number of printed matters.

[0017] [1] A lithographic printing plate precursor comprising ahydrophilic support having thereon a heat-sensitive layer containingeither a microcapsule containing a compound having a functional groupcapable of reacting by heat or a fine particulate polymer, wherein

[0018] (1) when the heat-sensitive layer contains a fine particulatepolymer, the fine particulate- polymer may be a fine particulate polymercapable of combining or incapable of combining by heat used for theimage formation and the fine particulate polymer has a functional groupcapable of reacting with a functional group present in another fineparticulate polymer or with a functional group present in anothercomponent in the heat-sensitive layer; or

[0019] (2) when the heat-sensitive layer contains a microcapsulecontaining a compound having a functional group capable of reacting byheat, the microcapsule may be a microcapsule having an outer wallcapable of rupturing or incapable of rupturing by heat used for theimage formation and a light-to-heat converting material is contained inthe heat-sensitive layer or in a layer adjacent thereto.

[0020] [2] The lithographic printing plate precursor as described in [1]above, comprising a hydrophilic support having provided thereon aheat-sensitive layer containing a fine particulate polymer capable ofcombining by heat, wherein the fine particulate polymer has a functionalgroup capable of reacting with a functional group present in anotherfine particulate polymer or with a functional group present in anothercomponent in the heat-sensitive layer.

[0021] [3] The lithographic printing plate precursor as described in [2]above, wherein the hydrophilic support is an aluminum substratesubjected to a surface roughening treatment and then to an anodizationtreatment.

[0022] [4] The lithographic printing plate precursor as described in [3]above, wherein the aluminum substrate is further subjected to a silicatetreatment.

[0023] [5] The lithographic printing plate precursor as described in [1]above, comprising a hydrophilic support having provided thereon aheat-sensitive layer containing a fine particulate polymer incapable ofcombining by heat used for the image formation, wherein the fineparticulate polymer has a functional group capable of reacting with afunctional group present in another fine particulate polymer or with afunctional group present in another component in the heat-sensitivelayer.

[0024] [6] The lithographic printing plate precursor as described in [5]above, wherein the hydrophilic support is an aluminum substratesubjected to a surface roughening treatment and then to an anodizationtreatment.

[0025] [7] The lithographic printing plate precursor as described in [6]above, wherein the aluminum substrate is further subjected to a silicatetreatment.

[0026] [8] The lithographic printing plate precursor as described in [1]above, comprising a hydrophilic support having thereon a heat-sensitivelayer comprising a microcapsule having an outer wall incapable ofrupturing by heat used for the image formation and containing a compoundhaving a functional group capable of reacting by heat, wherein alight-to-heat converting material is contained in the heat-sensitivelayer or in a layer adjacent thereto.

[0027] [9] The lithographic printing plate precursor as described in [8]above, wherein the compound diffused from the microcapsule is presenteither on the surface of the microcapsule or in the vicinity of thesurface.

[0028] [10] The lithographic printing plate precursor as described in[8] above, which is obtained by dispersing microcapsules each containinga compound having a functional group capable of reacting by heat in asolvent which swells the outer wall of the microcapsules, coating thedispersion solution on a hydrophilic support and drying the solution.

[0029] [11] The lithographic printing plate precursor as described in[8] above, wherein the hydrophilic support is an aluminum substratesubjected to a surface roughening treatment and then to an anodizationtreatment.

[0030] [12] The lithographic printing plate precursor as described in[11] above, wherein the aluminum substrate is further subjected to asilicate treatment.

[0031] [13] The lithographic printing plate precursor as described in[1] above, comprising a hydrophilic support having thereon aheat-sensitive layer comprising a microcapsule having an outer wallcapable of rupturing by heat used for the image information andcontaining a compound having a functional group capable of reacting bythe heat wherein a light-to-heat converting material is contained in theheat-sensitive layer or in a layer adjacent thereto.

[0032] [14] The lithographic printing plate precursor as described in[13] above, wherein the hydrophilic support is an aluminum substratesubjected to a surface roughening treatment and then to an anodizationtreatment.

[0033] [15] The lithographic printing plate precursor as described in[14] above, wherein the aluminum substrate is further subjected to asilicate treatment.

DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention is described in detail below.

[0035] [Fine Particulate Polymer Capable of Combining by Heat at ImageFormation]

[0036] The fine particulate polymer capable of combining by heat at theimage formation (hereinafter simply referred to as “fine particulatepolymer”), which is contained in the heat-sensitive layer of thelithographic printing plate precursor of the present invention, is notparticularly limited as long as it has a functional group capable ofreacting with a functional group present in another fine particulatepolymer or with a functional group present in another component in theheat-sensitive layer, however, examples thereof include latex containingthis functional group. The average particle size of the particles ispreferably from 0.01 to 20 μm, more preferably from 0.05 to 2.0 μm, mostpreferably from 0.06 to 0.40 μm. If the average particle size isexcessively large, bad resolution results, whereas if it is too small,the aging stability changes for the worse.

[0037] The fine particulate polymer may be reacted between fineparticles through a functional group or may be reacted with ahydrophilic resin or a low molecular compound added to theheat-sensitive layer. It is also possible to introduce foreignfunctional groups which are thermally reactive with each other, into twoor more kinds of fine particulate polymers and react the thermoplasticfine particulate polymers with each other. Examples of the reactionusing this functional group include a polymerization reaction of anunsaturated group, an addition reaction of an isocyanate group or ablock form thereof with a compound having an active hydrogen atom (forexample, amine, alcohol and carboxylic acid) , an addition reaction ofan epoxy group with an amino group, a carboxyl group or a hydroxylgroup, a condensation reaction of a carboxyl group with a hydroxyl groupor an amino group, and a ring opening addition reaction of an acidanhydride with an amino group or a hydroxyl group. As long as a chemicalbond can be formed, any of these reactions may be used.

[0038] The fine particulate polymer having this reactive functionalgroup is preferably a polymer in which an acrylate group, a methacrylategroup, a vinyl group, an allyl group, an epoxy group, an amino group, ahydroxyl group, a carboxyl group, an isocyanate, an acid anhydride or aprotective group thereof is present. This functional group may beintroduced at the time of polymerization or may be introduced using apolymer reaction after the polymerization.

[0039] In the case of introducing the group at the time ofpolymerization, a monomer having a functional group described above ispreferably emulsion polymerized or suspension polymerized. Specificexamples thereof include homopolymers and copolymers of a monomer suchas allyl methacrylate, allyl acrylate, vinyl methacrylate, vinylacrylate, glycidyl methacrylate, glycidyl acrylate, 2-isocyanate ethylmethacrylate or a block isocyanate thereof resulting from blocking withan alcohol, 2-isocyanate ethyl acrylate or a block isocyanate thereofresulting from blocking with an alcohol, 2-aminoethyl methacrylate,2-aminoethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxyethylacrylate, acrylic acid, methacrylic acid, maleic anhydride, diacrylateand dimethacrylate, however, the present invention is not limitedthereto. The copolymerizable monomer is not limited as long as it is amonomer not having a functional group related to the reaction, such asstyrene, alkyl acrylate, alkyl methacrylate, acrylonitrile and vinylacetate.

[0040] The functional group may also be introduced using a polymerreaction of the polymer. Examples thereof include the polymer reactiondescribed in WO96-34316.

[0041] Also, after dissolving the polymer having a reactive group in asolvent -and further dispersing the dissolved polymer in a water, thesolvent is evaporated to form the fine particulate polymer.

[0042] The fine particulate polymer capable of combining by heat at theimage formation preferably has a hydrophilic surface and is dispersiblein water. The film formed by coating only the fine particulate polymerand drying it at a temperature lower than the coagulation temperaturepreferably has a contact angle (aerial water droplet) lower than thecontact angle (aerial water droplet) of a film fusion-formed by dryingit at a temperature higher than the coagulation temperature. The surfaceof this fine particulate polymer may be rendered hydrophilic byadsorbing a hydrophilic polymer such as polyvinyl alcohol orpolyethylene glycol, an oligomer or a hydrophilic low molecular compoundto the fine particulate polymer surface, however, the method is notlimited thereto.

[0043] The coagulation temperature of the fine particulate polymercapable of combining by heat at the image formation is preferably 70° C.or more and on taking account of the aging stability, more preferably100° C. or more.

[0044] The fine particulate polymer capable of combining by heat at theimage formation is preferably added in an amount of 50 wt % or more,more preferably 60 wt % or more, based on the heat-sensitive layer. Ifthe amount added is less than this range, bad press life results.

[0045] [Fine Particulate Polymer Incapable of Combining by Heat Used forImage formation]

[0046] The fine particulate polymer incapable of combining by heat usedfor the image formation, which is contained in the heat-sensitive layerof the lithographic printing plate precursor of the present invention,is not particularly limited as long as it has a functional group capableof reacting with a functional group present in another fine particulatepolymer or with a functional group present in another component in theheat-sensitive layer, however, examples thereof include a latexcontaining this functional group. The average particle size of theparticles is preferably from 0.01 to 20 μm, more preferably from 0.05 to2.0 μm, most preferably from 0.06 to 0.40 μm. If the average particlesize is excessively large, bad resolution results, whereas if it is toosmall, the aging stability changes for the worse.

[0047] The fine particulate polymer may be reacted between fineparticles through a functional group or may be reacted with ahydrophilic resin as another additive in the heat-sensitive layer, whichis described later, or when a low molecular compound is contained, withthe low molecular compound. It is also possible to introduce foreignfunctional groups which are thermally reactive with each other, into twoor more kinds of fine particulate polymers and react the fineparticulate polymers with each other. Examples of the reaction usingthis functional group include a polymerization reaction of anunsaturated group, an addition reaction of an isocyanate group or ablock form thereof with a compound having an active hydrogen atom (forexample, amine, alcohol and carboxylic acid), an addition reaction of anepoxy group with an amino group, a carboxyl group or a hydroxyl group, acondensation reaction of a carboxyl group with a hydroxyl group or anamino group, and a ring opening addition reaction of an acid anhydridewith an amino group or a hydroxyl group. As long as a chemical bond canbe formed, any of these reactions may be used.

[0048] The fine particulate polymer having this reactive functionalgroup is preferably a polymer in which an acrylate group, a methacrylategroup, a vinyl group, an allyl group, an epoxy group, an amino group, ahydroxyl group, a carboxyl group, an isocyanate, an acid anhydride or aprotective group thereof is present. This functional group may beintroduced at the time of polymerization or may be introduced using apolymer reaction after the polymerization.

[0049] In the case of introducing the polymer at the time ofpolymerization, a monomer having a functional group described above ispreferably emulsion polymerized or suspension polymerized. Specificexamples thereof include homopolymers and copolymers of a monomer suchas allyl methacrylate, allyl acrylate, vinyl methacrylate, vinylacrylate, glycidyl methacrylate, glycidyl acrylate, 2-isocyanate ethylmethacrylate and a block form thereof resulting from blocking with analcohol, 2-isocyanate ethyl acrylate and a block form thereof resultingfrom blocking with an alcohol, 2-aminoethyl methacrylate, 2-aminoethylacrylate, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, acrylicacid, methacrylic acid, maleic anhydride, diacrylate and dimethacrylate,however, the present invention is not limited thereto. The monomer whichcan be copolymerized is not limited as long as it is a monomer nothaving a functional group related to the reaction, such as styrene,alkyl acrylate, alkyl methacrylate, acrylonitrile and vinyl acetate.However, a polyfunctional monomer is preferably introduced so as toprevent the polymer from combining by the heat generated uponirradiation of a laser ray. Specific examples of the polyfunctionalmonomer include acrylic acid esters such as ethylene glycol diacrylate,triethylene glycol diacrylate, 1,3-butanediol diacrylate, tetramethyleneglycol diacrylate, propylene glycol diacrylate, neopentyl glycoldiacrylate, trimethylolpropane triacrylate, trimethylolpropanetri-(acryloyloxypropyl) ether, trimethylolethane triacrylate, hexanedioldiacrylate, 1,4-cyclohexanediol diacrylate, tetraethylene glycoldiacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate,pentaerythritol tetraacrylate, dipentaerythritol diacrylate,dipentaerythritol hexaacrylate, sorbitol triacrylate, sorbitoltetraacrylate, sorbitol pentaacrylate, sorbitol hexaacrylate,tri-(acryloyloxyethyl)isocyanurate and polyester acrylate oligomer;

[0050] methacrylic acid esters such as tetramethylene glycoldimethacrylate, triethylene glycol dimethacrylate, neopentyl glycoldimethacrylate, trimethylolpropane trimethacrylate, trimethylolethanetrimethacrylate, ethylene glycol dimethacrylate, 1,3-butanedioldimethacrylate, hexanediol dimethacrylate, pentaerythritoldimethacrylate, pentaerythritol trimethacrylate, pentaerythritoltetramethacrylate, dipentaerythritol dimethacrylate, dipentaerythritolhexamethacrylate, sorbitol trimethacrylate, sorbitol tetramethacrylate,bis[p-(3-methacryloxy-2-hydroxypropoxy)phenyl]dimethylmethane andbis[p-(methacryloxyethoxy)phenyl]dimethylmethane;

[0051] itaconic acid esters such as ethylene glycol diitaconate,propylene glycol diitaconate, 1,3-butanediol diitaconate, 1,4-butanedioldiitaconate, tetramethylene glycol diitaconate, pentaerythritoldiitaconate and sorbitol tetraitaconate;

[0052] crotonic acid esters such as ethylene glycol dicrotonate,tetramethylene glycol dicrotonate, pentaerythritol dicrotonate andsorbitol tetradicrotonate;

[0053] isocrotonic acid esters such as ethylene glycol diisocrotonate,pentaerythritol diisocrotonate and sorbitol tetraisocrotonate; and

[0054] maleic acid esters such as ethylene glycol dimaleate, triethyleneglycol dimaleate, pentaerythritol dimaleate and sorbitol tetramaleate.

[0055] Other examples of the ester include aliphatic alcohol-basedesters described in JP-B-46-27926 (the term “JP-B” as used herein meansan “examined Japanese patent publication”), JP-B-51-47334 andJP-A-57-196231, esters having an aromatic skeleton described inJP-A-59-5240, JP-A-59-5241 and JP-A-2-226149, and esters containing anamino group described in JP-A-1-165613.

[0056] An amide monomer of an aliphatic polyhydric amine compound withan unsaturated carboxylic acid may also be used and specific examplesthereof include methylenebis-acrylamide, methylenebis-methacrylamide,1,6-hexamethylenebis-acrylamide, 1,6-hexamethylenebis-methacrylamide,diethylenetriaminetrisacrylamide, xylylenebisacrylamide andxylylenebismethacrylamide.

[0057] Other preferred examples of the amide-type monomer include thosehaving a cyclohexylene structure described in JP-B-54-21726.

[0058] A urethane-based addition polymerizable compound produced byusing an addition reaction of an isocyanate with a hydroxyl group isalso suitably used and specific examples thereof include vinyl urethanecompounds having two or more polymerizable vinyl groups within onemolecule described in JP-B-48-41708, which are obtained by adding avinyl monomer having a hydroxyl group represented by the followingformula (A) to a polyisocyanate compound having two or more isocyanategroups within one molecule:

CH₂═C(R₄₁)COOCH₂CH(R₄₂)OH  (A)

[0059] (wherein R₄₁ and R₄₂ each represents H or CH₃)

[0060] Also, urethane acrylates described in JP-A-51-37193, JP-B-2-32293and JP-B-2-16765, and urethane compounds having an ethylene oxide-typeskeleton described in JP-B-58-49860, JP-B-56-17654, JP-B-62-39417 andJP-B-62-39418 may be suitably used.

[0061] Furthermore, radical polymerizable compounds having an amino orsulfide structure within the molecule described in JP-A-63-277653,JP-A-63-260909 and JP-A-1-105238 may be used.

[0062] Other examples include polyfunctional acrylates and methacrylatessuch as polyester acrylates described in JP-A-48-64183, JP-B-49-43191and JP-B-52-30490 and epoxy acrylates obtained by reacting an epoxyresin with a (meth)acrylic acid. In addition, specific unsaturatedcompounds described in JP-B-46-43946, JP-B-1-40337 and JP-B-1-40336, andvinyl phosphonic acid-based compounds described in JP-A-2-25493 may beused. In some cases, structures containing a perfluoroalkyl groupdescribed in JP-A-61-22048 are suitably used. Furthermore, thosedescribed as a photocurable monomer or oligomer in Nippon SecchakuKyokaishi (Journal of Japan Adhesive Society), Vol. 20, No. 7, pp.300-308 (1984) may also be used.

[0063] The functional group may also be introduced using a polymerreaction of the polymer. Examples thereof include the polymer reactiondescribed in WO96-34316.

[0064] The fine particulate polymer containing this functional groupcapable of chemically combining by heat preferably has a hydrophilicsurface and is dispersible in water. The surface of this fineparticulate polymer may be rendered hydrophilic by adsorbing ahydrophilic polymer such as polyvinyl alcohol or polyethylene glycol, anoligomer or a hydrophilic low molecular compound to the fine particulatepolymer surface, however, the met-hod is not limited thereto.

[0065] The fine particulate polymer containing a functional groupcapable of combining by heat is preferably added in an amount of 50 wt %or more, more preferably 60 wt % or more, based on the heat-sensitivelayer.

[0066] [Microcapsule Having Outer Wall Incapable of Rupturing by Heat]

[0067] The microcapsule for use in the present invention has an outerwall incapable of rupturing by heat used for the image formation andcontains a compound having a functional group capable of reacting by theheat. The average particle size thereof is preferably from 0.01 to 20μm, more preferably from 0.05 to 2.0 μm, most preferably from 0.06 to0.40 μm. If the average particle size is excessively large, badresolution results, whereas if it is too small, the aging stabilitychanges for the worse.

[0068] The microcapsule may have a structure such that microcapsules canreact with each other through a thermally reactive group of theabove-described compound contained therein or in the case where ahydrophilic resin or a low molecular compound, which are describedlater, is contained as another additive in the heat-sensitive layer, themicrocapsule may have a structure such that the microcapsule can reactwith the hydrophilic resin or low molecular compound. Also, thermallyreactive groups capable of thermally reacting with each other may beintroduced into two or more kinds of microcapsules to have a structuresuch that the microcapsules can react with each other. Examples of thereaction using this thermally reactive group include a polymerizationreaction of an unsaturated group, an addition reaction of an isocyanategroup or a block form thereof with a compound having an active hydrogenatom (for example, amine, alcohol and carboxylic acid), an additionreaction of an epoxy group with an amino group, a carboxyl group or ahydroxyl group, a condensation reaction of a carboxyl group with ahydroxyl group or an amino group, and a ring opening addition reactionof an acid anhydride with an amino group or a hydroxyl group. As long asa chemical bond can be formed, any of these reactions may be used.

[0069] The microcapsule containing a compound having the thermallyreactive group may be obtained by a method of encapsulating a compound(which is described in detail later) having a thermally reactive groupsuch as an acrylate group, a methacrylate group, a vinyl group, an allylgroup, an epoxy group, an amino group, a hydroxyl group, a carboxylgroup, an isocyanate, an acid anhydride or a protective group thereof,or introducing this compound into the outer wall of a microcapsule. Atthe same time with the encapsulation of the compound having a thermallyreactive group, the compound may be introduced into the outer wall ofthe microcapsule.

[0070] Examples of the compound having a thermally reactive group, whichcan be encapsulated, include compounds having an unsaturated group. Thecompound having an unsaturated group is a radical polymerizable compoundhaving at least one ethylenically unsaturated double bond, and selectedfrom the compounds having at least one, preferably two or moreethylenically unsaturated - terminal bonds. Such compounds are widelyknown in this industrial field and those known compounds all can be usedin the present invention without any limit. This compound has a chemicalform of, for example, monomer, prepolymer, more specifically, dimer,trimer or oligomer, a mixture thereof or a copolymer thereof. Examplesof the monomer and its copolymer include unsaturated carboxylic acids(e.g., acrylic acid, methacrylic acid, itaconic acid, crotonic acid,isocrotonic acid, maleic acid) , and esters and amides thereof. Amongthese, preferred are esters of an unsaturated carboxylic acid with analiphatic polyhydric alcohol compound, and amides of an unsaturatedcarboxylic acid with an aliphatic polyhydric amine compound. Also,addition reaction products of an unsaturated carboxylic acid ester oramide having a nucleophilic substituent such as hydroxyl group, aminogroup or mercapto group with a monofunctional or polyfunctionalisocyanate or epoxy, and dehydration condensation reaction products witha monofunctional or polyfunctional carboxylic acid may be suitably used.Furthermore, addition reaction products of an unsaturated carboxylicacid ester or amide having an electrophilic substituent such asisocyanate group or epoxy group with a monofunctional or polyfunctionalalcohol, amine or thiol, and substitution reaction products of anunsaturated carboxylic acid ester or amide having an eliminatingsubstituent such as halogen group or tosyloxy group with amonofunctional or polyfunctional alcohol, amine or thiol may also besuitably used. These compounds but where the unsaturated carboxylic acidis replaced by an unsaturated phosphonic acid, styrene, vinyl ether orthe like may also be used.

[0071] Specific examples of the radical polymerizable compound which isan ester of an aliphatic polyhydric alcohol compound with an unsaturatedcarboxylic acid include acrylic acid esters such as ethylene glycoldiacrylate, triethylene glycol diacrylate, 1,3-butanediol diacrylate,tetramethylene glycol diacrylate, propylene glycol diacrylate, neopentylglycol diacrylate, trimethylolpropane triacrylate, trimethylolpropanetri-(acryloyloxypropyl) ether, trimethylolethane triacrylate, hexanedioldiacrylate, 1,4-cyclohexanediol diacrylate tetraethylene glycoldiacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate,pentaerythritol tetraacrylate, dipentaerythritol diacrylate,dipentaerythritol hexaacrylate, sorbitol triacrylate, sorbitoltetraacrylate, sorbitol pentaacrylate, sorbitol hexaacrylate,tri-(acryloyloxyethyl)isocyanurate and polyester acrylate oligomer;

[0072] methacrylic acid esters such as tetramethylene glycoldimethacrylate, triethylene glycol dimethacrylate, neopentyl glycoldimethacrylate, trimethylolpropane trimethacrylate, trimethylolethanetrimethacrylate, ethylene glycol dimethacrylate, 1,3-butanedioldimethacrylate, hexanediol dimethacrylate, pentaerythritoldimethacrylate, pentaerythritol trimethacrylate, pentaerythritoltetramethacrylate, dipentaerythritol dimethacrylate, dipentaerythritolhexamethacrylate, sorbitol trimethacrylate, sorbitol tetramethacrylate,bis[p-(3-methacryloxy-2-hydroxypropoxy)phenyl]dimethylmethane andbis[p-(methacryloxyethoxy)phenyl]dimethylmethane;

[0073] itaconic acid esters such as ethylene glycol diitaconate,propylene glycol diitaconate, 1,3-butanediol diitaconate, 1,4-butanedioldiitaconate, tetramethylene glycol diitaconate, pentaerythritoldiitaconate and sorbitol tetraitaconate;

[0074] crotonic acid esters such as ethylene glycol dicrotonate,tetramethylene glycol dicrotonate, pentaerythritol dicrotonate andsorbitol tetradicrotonate;

[0075] isocrotonic acid esters such as ethylene glycol diisocrotonate,pentaerythritol diisocrotonate and sorbitol tetraisocrotonate; and

[0076] maleic acid esters such as ethylene glycol dimaleate, triethyleneglycol dimaleate, pentaerythritol dimaleate and sorbitol tetramaleate.

[0077] Other examples of the ester include aliphatic alcohol-basedesters described in JP-B-46-27926, JP-B-51-47334 and JP-A-57-196231,those having an aromatic skeleton described in JP-A-59-5240,JP-A-59-5241 and JP-A-2-226149, and those containing an amino groupdescribed in JP-A-1-165613.

[0078] Specific examples of the amide monomer of an aliphatic polyhydricamine compound with an unsaturated carboxylic acid includemethylenebis-acrylamide, methylenebis-methacrylamide,1,6-hexamethylenebis-acrylamide, 1,6-hexamethylenebis-methacrylamide,diethylenetriaminetris-acrylamide, xylylenebisacrylamide andxylylenebis-methacrylamide.

[0079] Other preferred examples of the amide-type monomer include thosehaving a cyclohexylene structure described in JP-B-54-21726.

[0080] A urethane-based addition polymerizable compound produced byusing an addition reaction of isocyanate and a hydroxyl group may alsobe suitably used and specific examples thereof include vinyl urethanecompounds having two or more polymerizable vinyl groups within onemolecule described in JP-B-48-41708, which are obtained by adding avinyl monomer having a hydroxyl group represented by the followingformula (A) to a polyisocyanate compound having two or more isocyanategroups within one molecule:

CH₂═C(R₄₁)COOCH₂CH(R₄₂)OH  (A)

[0081] (wherein R₄₁ and R₄₂ each represents H or CH₃).

[0082] Also, urethane acrylates described in JP-A-51-37193, JP-B-2-32293and JP-B-2-16765, and urethane compounds having an ethylene oxide-typeskeleton described in JP-B-58-49860, JP-B-56-17654, JP-B-62-39417 andJP-B-62-39418 are also suitably used.

[0083] Furthermore, radical polymerizable compounds having an amino orsulfide structure within the molecule described in JP-A-63-277653,JP-A-63-260909 and JP-A-1-105238 may be used.

[0084] Other examples include polyfunctional acrylates and methacrylatessuch as polyester acrylates described in JP-A-48-64183, JP-B-49-43191and JP-B-52-30490 and epoxy acrylates obtained by reacting an epoxyresin with a (meth)acrylic acid. In addition, specific unsaturatedcompounds described in JP-B-46-43946, JP-B-1-40337 and JP-B-1-40336, andvinyl phosphonic acid-based compounds described in JP-A-2-25493 may beused. In some cases, structures containing a perfluoroalkyl groupdescribed in JP-A-61-22048 are suitably used. Furthermore, thosedescribed as a photocurable monomer or oligomer in Nippon SecchakuKyokaishi (Journal of Japan Adhesive Society), Vol. 20, No. 7, pp.300-308 (1984) may also be used.

[0085] Preferred examples of the epoxy compound include glycerinpolyglycidyl ether, polyethylene glycol diglycidyl ether, polypropylenediglycidyl ether, trimethylol propane polyglycidyl ether, sorbitolpolyglycidyl ether, bisphenols, polyphenols and hydrogenated productsthereof, namely, polyglycidyl ether forms thereof.

[0086] Preferred examples of the compound having an isocyanate includetolylene diisocyanate, diphenylmethane diisocyanate, polymethylenepolyphenyl polyisocyanate, xylylene diisocyanate, naphthalenediisocyanate, cyclohexane phenylene diisocyanate, isophoronediisocyanate, hexamethylene diisocyanate, cyclohexyl diisocyanate andblocked compounds thereof with an alcohol or an amine. Preferredexamples of the amine compound include ethylenediamine,diethylenetriamine, triethylenetetramine, hexamethylenediamine,propylenediamine and polyethyleneimine.

[0087] Preferred examples of the compound having a hydroxyl groupinclude compounds having a terminal methylol, polyhydric alcohols suchas pentaerythritol, bisphenols and polyphenols.

[0088] Preferred examples of the compound having a carboxyl groupinclude aromatic polyhydric carboxylic acids such as pyromellitic acid,trimellitic acid and phathalic acid, and aliphatic polyhydric carboxylicacids such as adipic acid.

[0089] Preferred examples of the acid anhydride include pyromelliticacid anhydride and benzophenonetetracarboxylic acid anhydride.

[0090] In the lithographic printing plate precursor of the presentinvention, the compound having a thermally reactive group is preferablyallowed to diffuse from the microcapsule and be present at least eitheron the surface thereof or in the vicinity of the surface, whereby thecompound causes a chemical reaction by heat at the image formation andthen the molecular structure in the image area of the heat-sensitivelayer changes into a three-dimensional crosslinked form. As a resultthereof, the solubility of the image area in water or an aqueoussolution greatly differs between before and after the image formationand even after aging, the plate can exhibit good on-pressdevelopability. Furthermore, the microcapsule used has an outer wallwhich does not rupture by heat used for the image formation, therefore,even after the image formation, the microcapsule can be present as aparticle in the image area and by virtue of this, the image area canhave strong strength, as a result, a larger number of printed matterscan be obtained. Incidentally, microcapsules having an outer wall whichruptures by heat generated at the time of image formation, are poor inthe aging stability.

[0091] For allowing the compound having a thermally reactive group todiffuse from a microcapsule in the heat-sensitive layer and be presenton the surface of the microcapsule and in the vicinity of the surface,for example, the microcapsules may be dispersed in a solvent whichswells the outer wall of the microcapsule.

[0092] To this purpose, the material for the outer wall of themicrocapsule for use in the present invention preferably has athree-dimensional crosslink and has properties of swelling by a solvent.In view of these, the wall material of the microcapsule is preferablypolyurea, polyurethane, polyester, polycarbonate, polyamide or a mixturethereof, more preferably polyurea or polyurethane. Into the outer wallof the microcapsule, as described above, the compound having a thermallyreactive group may be introduced.

[0093] For encapsulating the compound having a thermally reactive group,conventionally known encapsulation methods may be used. Examples of themethod for producing a microcapsule include -a method using coacervationdescribed in U.S. Pat. Nos. 2,800,457 and 2,800,458, a method usinginterfacial polymerization methods described in British Patent 990,443,U.S. Pat. No. 3,287,154, JP-B-38-19574, JP-B-42-446 and JP-B-42-771, amethod using polymer precipitation described in U.S. Pat. Nos. 3,418,250and 3,660,304, a method using an isocyanate polyol wall materialdescribed in U.S. Pat. No. 3,796,669, a method using an isocyanate wallmaterial described in U.S. Pat. No. 3,914,511, a method using aurea-formaldehyde or urea-formaldehyde-resorcinol wall materialdescribed in U.S. Pat. Nos. 4,001,140, 4,087,376 and 4,089,802, a methodusing a wall material such as melamine-formaldehyde resin or hydroxycellulose described in U.S. Pat. No. 4,025,455, an in situ method usingmonomer polymerization described in JP-B-36-9168 and JP-A-51-9079, aspray drying method described in British Patent 930,422 and U.S. Pat.No. 3,111,407, and an electrolytic dispersion cooling method describedin British Patents 952,807 and 965,074. However, the present inventionis not limited thereto.

[0094] The solvent which swells the outer wall of the microcapsuledepends on the microcapsule-dispersing solvent (called a solvent or acoating solution), the constructive material and wall thickness of themicrocapsule wall, and the compound having a thermally reactive groupcontained in the microcapsule, however, the solvent may be easilyselected from a large number of commercially available solvents. Forexample, in the case of a water-dispersible microcapsule comprising acrosslinked polyurea or polyurethane wall, preferred examples of thesolvent include alcohols, ethers, acetals, esters, ketones, polyhydricalcohols, amides, amines and aliphatic acids.

[0095] Specific examples thereof include methanol, ethanol, tertiarybutanol, n-propanol, tetrahydrofurane, methyl lactate, ethyl lactate,methyl ethyl ketone, propylene glycol monomethyl ether, ethylene glycoldiethyl ether, ethylene glycol monomethyl ether, γ-butyllactone,N,N-dimethylformamide and N,N-dimethylacetamide, however, the presentinvention is not limited thereto. These solvents may be used incombination of two or more thereof.

[0096] A solvent which does not dissolve in the microcapsule-dispersingsolvent but dissolves when mixed with the above-described solvent, mayalso be used.

[0097] The amount added of the solvent which swells the outer wall ofthe microcapsule is determined by the combination of raw materials,however, if the amount added is less than the optimum value, the imageformation proceeds insufficiently, whereas if it exceeds the optimumvalue, the dispersion solution deteriorates in the stability. Usually,the amount of the solvent added is effectively from 5 to 95 wt %,preferably from 10 to 90 wt %, more preferably from 15 to 85 wt %, basedon the coating solution.

[0098] For measuring the compound having a thermally reactive group,which is present on the microcapsule or in the vicinity thereof,conventional surface measurement techniques using X-ray photoelectricspectrometry (i.e., Electron Spectroscopy for Chemical Analysis: ESCA)may be used.

[0099] The microcapsule is added in an amount of preferably 50% by weighor more, more preferably 60% by weight or more, based on theheat-sensitive layer.

[0100] If the amount of the microcapsule is less than 50% by weight, thepress life is deteriorated.

[0101] [Microcapsule Having Outer Wall Capable of Rupturing by Heat]

[0102] The microcapsule for use in the present invention has an outerwall capable of rupturing by heat used for the image formation andcontains a compound having a functional group capable of reacting by theheat (also called a thermally reactive group). The average particle sizethereof is preferably from 0.01 to 20 μm, more preferably from 0.05 to2.0 μm, most preferably from 0.06 to 0.40 μm. If the average particlesize is excessively large, bad resolution results, whereas if it is toosmall, the aging stability changes for the worse.

[0103] The microcapsule may have a structure such that microcapsules canreact with each other through a thermally reactive group of theabove-described compound contained therein or in the case where ahydrophilic resin or a low molecular compound, which are describedlater, is contained as another additive in the heat-sensitive layer, themicrocapsule may have a structure such that the microcapsule can reactwith the hydrophilic resin or low molecular compound. Also, thermallyreactive groups capable of thermally reacting with each other may beintroduced into two or more kinds of microcapsules to have a structuresuch that the microcapsules can react with each other. Examples of thereaction using this thermally reactive group include a polymerizationreaction of an unsaturated group, an addition reaction of an isocyanategroup or a block form thereof with a compound having an active hydrogenatom (for example, amine, alcohol and carboxylic acid), an additionreaction of an epoxy group with an amino group, a carboxyl group or ahydroxyl group, a condensation reaction of a carboxyl group with ahydroxyl group or an amino group, and a ring opening addition reactionof an acid anhydride with an amino group or a hydroxyl group. As long asa chemical bond can be formed, any of these reactions may be used.

[0104] The microcapsule containing a compound having the thermallyreactive group may be obtained by a method of encapsulating a compound(which is described in detail later) having a thermally reactive groupsuch as an acrylate group, a methacrylate group, a vinyl group, an allylgroup, an epoxy group, an amino group, a hydroxyl group, a carboxylgroup, an isocyanate, an acid anhydride or a protective group thereof,or introducing this compound into the outer wall of a microcapsule. Atthe same time with the encapsulation of the compound having a thermallyreactive group, the compound may be introduced into the outer wall ofthe microcapsule.

[0105] Examples of the compound having a thermally reactive group, whichcan be encapsulated, include compounds having an unsaturated group. Thecompound having an unsaturated group is a radical polymerizable compoundhaving at least one ethylenically unsaturated double bond, and selectedfrom the compounds having at least one, preferably two or moreethylenically unsaturated terminal bonds. Such compounds are widelyknown in this industrial field and those known compounds all can be usedin the present invention without any limit. This compound has a chemicalform of, for example, monomer, prepolymer, more specifically, dimer,trimer or oligomer, a mixture thereof or a copolymer thereof. Examplesof the monomer and its copolymer include unsaturated carboxylic acids(e.g., acrylic acid, methacrylic acid, itaconic acid, crotonic acid,isocrotonic acid, maleic acid), and esters and amides thereof. Amongthese, preferred are esters of an unsaturated carboxylic acid with analiphatic polyhydric alcohol compound, and amides of an unsaturatedcarboxylic acid with an aliphatic polyhydric amine compound. Also,addition reaction products of an unsaturated carboxylic acid ester oramide having a nucleophilic substituent such as hydroxyl group, aminogroup or mercapto group with a monofunctional or polyfunctionalisocyanate or epoxy, and dehydration condensation reaction products witha monofunctional or polyfunctional carboxylic acid may be suitably used.Furthermore, addition reaction products of an unsaturated carboxylicacid ester or amide having an electrophilic substituent such asisocyanate group or epoxy group with a monofunctional or polyfunctionalalcohol, amine or thiol, and substitution reaction products of anunsaturated carboxylic acid ester or amide having a splitting-offsubstituent such as halogen group or tosyloxy group with amonofunctional or polyfunctional alcohol, amine or thiol may also besuitably used. These compounds but where the unsaturated carboxylic acidis replaced by an unsaturated phosphonic acid, styrene or the like, mayalso be used.

[0106] Specific examples of the radical polymerizable compound which isan ester of an aliphatic polyhydric alcohol compound with an unsaturatedcarboxylic acid include acrylic acid esters such as ethylene glycoldiacrylate, triethylene glycol diacrylate, 1,3-butanediol diacrylate,tetramethylene glycol diacrylate, propylene glycol diacrylate, neopentylglycol diacrylate, trimethylolpropane triacrylate, trimethylolpropanetri-(acryloyloxypropyl) ether, trimethylolethane triacrylate, hexanedioldiacrylate, 1,4-cyclohexanediol diacrylate, tetraethylene glycoldiacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate,pentaerythritol tetraacrylate, dipentaerythritol diacrylate,dipentaerythritol hexaacrylate, sorbitol triacrylate, sorbitoltetraacrylate, sorbitol pentaacrylate, sorbitol hexaacrylate,tri-(acryloyloxyethyl)isocyanurate and polyester acrylate oligomer;

[0107] methacrylic acid esters such as tetramethylene glycoldimethacrylate, triethylene glycol dimethacrylate, neopentyl glycoldimethacrylate, trimethylolpropane trimethacrylate, trimethylolethanetrimethacrylate, ethylene glycol dimethacrylate, 1,3-butanedioldimethacrylate, hexanediol dimethacrylate, pentaerythritoldimethacrylate, pentaerythritol trimethacrylate, pentaerythritoltetramethacrylate, dipentaerythritol dimethacrylate, dipentaerythritolhexamethacrylate, sorbitol trimethacrylate, sorbitol tetramethacrylate,bis[p-(3-methacryloxy-2-hydroxypropoxy)phenyl]dimethylmethane and bis[p-(methacryloxyethoxy)phenyl]dimethylmethane;

[0108] itaconic acid esters such as ethylene glycol diitaconate,propylene glycol diitaconate, 1,3-butanediol diitaconate, 1,4-butanedioldiitaconate, tetramethylene glycol diitaconate, pentaerythritoldiitaconate and sorbitol tetraitaconate;

[0109] crotonic acid esters such as ethylene glycol dicrotonate,tetramethylene glycol dicrotonate, pentaerythritol dicrotonate andsorbitol tetradicrotonate;

[0110] isocrotonic acid esters such as ethylene glycol diisocrotonate,pentaerythritol diisocrotonate and sorbitol tetraisocrotonate; and

[0111] maleic acid esters such as ethylene glycol dimaleate, triethyleneglycol dimaleate, pentaerythritol dimaleate and sorbitol tetramaleate.

[0112] Other examples of the ester include aliphatic alcohol-basedesters described in JP-B-46-27926, JP-B-51-47334 and JP-A-57-196231,those having an aromatic skeleton described in JP-A-59-5240,JP-A-59-5241 and JP-A-2-226149, and those containing an amino groupdescribed in JP-A-1-165613.

[0113] Specific examples of the amide monomer of an aliphatic polyhydricamine compound with an unsaturated carboxylic acid includemethylenebis-acrylamide, methylenebis-methacrylamide,1,6-hexamethylenebis-acrylamide, 1,6-hexamethylenebis-methacrylamide,diethylenetriaminetris-acrylamide, xylylenebisacrylamide andxylylenebis-methacrylamide.

[0114] Other preferred examples of the amide-type monomer include thosehaving a cyclohexylene structure described in JP-B-54-21726.

[0115] A urethane-based addition polymerizable compound produced byusing an addition reaction of isocyanate and a hydroxyl group may alsobe suitably used and specific examples thereof include vinyl urethanecompounds having two or more polymerizable vinyl groups within onemolecule described in JP-B-48-41708, which are obtained by adding avinyl monomer having a hydroxyl group represented by the followingformula (A) to a polyisocyanate compound having two or more isocyanategroups within one molecule:

CH₂═C(R₄₁)COOCH₂CH(R₄₂)OH  (A)

[0116] (wherein R₄₁ and R₄₂ each represents H or CH₃)

[0117] Also, urethane acrylates described in JP-A-51-37193, JP-B-2-32293and JP-B-2-16765, and urethane compounds having an ethylene oxide-typeskeleton described in JP-B-58-49860, JP-B-56-17654, JP-B-62-39417 andJP-B-62-39418 are also suitably used.

[0118] Furthermore, radical polymerizable compounds having an amino orsulfide structure within the molecule described in JP-A-63-277653,JP-A-63-260909 and JP-A-1-105238 may be used.

[0119] Other examples include polyfunctional acrylates and methacrylatessuch as polyester acrylates described in JP-A-48-64183, JP-B-49-43191and JP-B-52-30490 and epoxy acrylates obtained by reacting an epoxyresin with a (meth)acrylic acid. In addition, specific unsaturatedcompounds described in JP-B-46-43946, JP-B-1-40337 and JP-B-1-40336, andvinyl phosphonic acid-based compounds described in JP-A-2-25493 may beused. In some cases, structures containing a perfluoroalkyl groupdescribed in JP-A-61-22048 are suitably used. Furthermore, thosedescribed as a photocurable monomer or oligomer in Nippon SecchakuKyokaishi (Journal of Japan Adhesive Society), Vol. 20, No. 7, pp.300-308 (1984) may also be used.

[0120] Preferred examples of the epoxy compound include glycerinpolyglycidyl ether, polyethylene glycol diglycidyl ether, polypropylenediglycidyl ether, trimethylol propane polyglycidyl ether, sorbitolpolyglycidyl ether, bisphenols, polyphenols and hydrogenated productsthereof, namely, polyglycidyl ether forms thereof.

[0121] Preferred examples of the compound having an isocyanate includetolylene diisocyanate, diphenylmethane diisocyanate, polymethylenepolyphenyl polyisocyanate, xylylene diisocyanate, naphthalenediisocyanate, cyclohexane phenylene diisocyanate, isophoronediisocyanate, hexamethylene diisocyanate, cyclohexyl diisocyanate andblocked compounds thereof with an alcohol or an amine. Preferredexamples of the amine compound include ethylenediamine,diethylenetriamine, triethylenetetramine, hexamethylenediamine,propylenediamine and polyethyleneimine.

[0122] Preferred examples of the compound having a hydroxyl groupinclude compounds having a terminal methylol, polyhydric alcohols suchas pentaerythritol, bisphenols and polyphenols.

[0123] Preferred examples of the compound having a carboxyl groupinclude aromatic polyhydric carboxylic acids such as pyromellitic acid,trimellitic acid and phathalic acid, and aliphatic polyhydric carboxylicacids such as adipic acid.

[0124] Preferred examples of the acid anhydride include pyromelliticacid anhydride and benzophenonetetracarboxylic acid anhydride.

[0125] In the lithographic printing plate precursor of the presentinvention, microcapsules containing the compound having a thermallyreactive group are incorporated into the heat-sensitive layer, wherebythe outer wall of the microcapsule ruptures by the heat at the time ofimage formation, the compound contained in the microcapsule is releasedinto the heat-sensitive layer and causes a chemical reaction, andthereby the molecular structure in the image area of the heat-sensitivelayer changes into a three-dimensional crosslinked form. As a resultthereof, the solubility of the image area in water or an aqueoussolution greatly differs between before and after the image formation,and good on-press developability can be exhibited. Furthermore, themicrocapsule used has an outer wall which ruptures by heat used for theimage formation, therefore, the compound can thermally react with thecompound outside the microcapsule without fail and the crosslinkingdensity of the three-dimensional crosslinked form is considered to bevery high. By virtue of this, the image obtained after the imageformation can have high strength and thereby, a larger number of printedmatters can be obtained.

[0126] The material for the outer wall of the microcapsule for use inthe present invention is preferably polyurea, polyurethane, polyester,polycarbonate, polyamide or a mixture thereof, more preferably polyureaor polyurethane. Into the outer wall of the microcapsule, as describedabove, the compound having a thermally reactive group may be introduced.

[0127] For encapsulating the compound having a thermally reactive group,conventionally known encapsulation methods may be used. Examples of themethod for producing a microcapsule include a method using coacervationdescribed in U.S. Pat. Nos. 2,800,457 and 2,800,458, a method usinginterfacial polymerization methods described in British Patent 990,443,U.S. Pat. No. 3,287,154, JP-B-38-19574, JP-B-42-446 and JP-B-42-771, amethod using polymer precipitation described in U.S. Pat. Nos.3,418,1250 and 3,660,304, a method using an isocyanate polyol wallmaterial described in U.S. Pat. No. 3,796,669, a method using anisocyanate wall material described in U.S. Pat. No. 3,914,511, a methodusing a urea-formaldehyde or urea-formaldehyde-resorcinol wall materialdescribed in U.S. Pat. Nos. 4,001,140, 4,087,376 and 4,089,802, a methodusing a wall material such as melamine-formaldehyde resin or hydroxycellulose described in U.S. Pat. No. 4,025,455, an in situ method usingmonomer polymerization described in JP-B-36-9168 and JP-A-51-9079, aspray drying method described in British Patent 930,422 and U.S. Pat.No. 3,111,407, and an electrolytic dispersion cooling method describedin British Patents 952,807 and 965,074. However, the present inventionis not limited thereto.

[0128] The microcapsule is added in an amount of preferably 50% byweight or more, more preferably 60% by weight or more, based on theheatt-sensitive layer.

[0129] If the amount of the microcapsule is less than 50% by weight, thepress life is deteriorated.

[0130] [Light-to-Heat Converting Material]

[0131] When a light-to-heat converting material is incorporated into theheat-sensitive layer or a layer adjacent thereto, the lithographicprinting plate precursor of the present invention can perform writing ofan image by the irradiation of a laser light or the like.

[0132] In the case where a microcapsule having an outer wall incapableof rupturing by heat used for the image formation is used in theheat-sensitive layer, the light-to-heat converting material ispreferably contained within the microcapsule so as to attain effectiveuse of the heat generated from the light-to-heat converting material.When the light-to-heat converting material is contained within themicrocapsule, the elevation of heat occurs from the inside of themicrocapsule, therefore, the heat can be effectively used for thepermeation and bleeding out of the encapsulated substance through theouter wall of the microcapsule or for activating the reaction of thereactive substance, whereby the lithographic printing plate precursor ofthe present invention can be improved in the press life.

[0133] In the case where a microcapsule having an outer wall capable ofrupturing by heat used for the image formation is used in theheat-sensitive layer, the light-to-heat converting material ispreferably contained within the microcapsule so as to attain effectiveuse of the heat generated from the light-to-heat converting material.When the light-to-heat converting material is contained within themicrocapsule, the heat can be effectively used for the rupture of theouter wall of the microcapsule, release of the encapsulated substance,and activation of the reaction of the reactive substance, whereby thelithographic printing plate precursor of the present invention can beimproved in the press life.

[0134] In the case where a microcapsule having an outer wall capable ofrupturing by heat or a fine particulate polymer capable of combining byheat is used in the heat-sensitive layer, the light-to-heat convertingmaterial is preferably contained within the microcapsule or the fineparticulate polymer so as to attain effective use of the heat generatedfrom the light-to-heat converting material. When the light-to-heatconverting material is contained within the microcapsule or fineparticulate polymer, the heat can be effectively used for the rupture ofthe outer wall of the microcapsule, release of the encapsulatedsubstance, and activation of the reaction of the reactive substance,whereby the lithographic printing plate precursor of the presentinvention can be improved in the press life.

[0135] The light-to-heat converting material is not particularly limitedas long as it absorbs light in the wavelength region of the lightsource, and examples thereof include carbon black, fine particulatemetal and dye. In particular, compounds which absorb infrared light andconverts it into heat are preferred.

[0136] The light-to-heat converting material is particularly preferablya substance which absorbs light at 700 nm or more and various pigmentsand dyes can be used. Examples of the pigment which can be used includecommercially available pigments and pigments described in Color Index(C.I.) Binran (C.I. Handbook), Saishin Ganryo Binran (Handbook of NewestPigments), compiled by Nippon Ganryo Gijutsu Kyokai (1977), SaishinGanryo Oyo Gijutsu (Up-To-Date Pigment Application Technology), CMC(1986), and Insatsu Ink Gijutsu (Printing Ink Technology), CMC (1984).

[0137] The kind of pigment includes black pigment, brown pigment, redpigment, violet pigment, blue pigment, green pigment, fluorescentpigment, metal powder pigment and polymer bond pigment. Specificexamples of the pigment which can be used include insoluble azopigments, azo lake pigments, condensed azo pigments, chelate azopigments, phthalocyanine-based pigments, anthraquinone-based pigments,perylene- and perynone-based pigments, thioindigo-based pigments,quinacridone-based pigments, dioxazine-based pigments,isoindolinone-based pigments, quinophthalone-based pigments, dyed lakepigments, azine pigments, nitroso pigments, nitro pigments, naturalpigments, fluorescent pigments, inorganic pigments and carbon black.

[0138] These pigments may or may not be surface-treated before use. Forthe surface treatment, a method of coating a hydrophilic or lipophilicresin on the surface, a method of attaching a surfactant, and a methodof bonding a reactive substance (for example, silica sol, alumina sol,silane coupling agent, epoxy compound or isocyanate compound) to thepigment surface may be used. These surface treatment methods aredescribed in Kinzoku Sekken no Seishitsu to Oyo (Properties andApplication of Metal Soap), Saiwai Shobo, Insatsu Ink Gijutsu (PrintingInk Technology), CMC (1984), and Saishin Ganryo Oyo Gijutsu (Up-To-DatePigment Application Technology), CMC (1986). Among these pigments, thosewhich absorb infrared light or near infrared light are preferred becausethese are suitable for the use with a laser which emits infrared lightor near infrared light.

[0139] Suitable examples of the pigment which absorbs infrared light ornear infrared light include carbon pigment, hydrophilic resin-coatedcarbon black and silica sol-modified carbon black. Among these, carbonblack having a surface coated with hydrophilic resin or silica sol isuseful because of easy dispersibility in a water-soluble resin andfreeness of impairment in the hydrophilicity.

[0140] The particle size of the pigment is preferably from 0.01 to 1 μm,more preferably from 0.01 to 0.5 μm. For dispersing the pigment, a knowndispersion technique for use in the production of ink or toner may beused. Examples of the disperser include ultrasonic disperser, sand mill,attritor, pearl mill, super-mill, ball mill, impeller, disperser, KDmill, colloid mill, dynatron, three-roll mill and pressure kneader.These are described in detail in Saishin Ganryo Oyo Gijutsu (Up-To-DatePigment Application Technology), CMC (1986).

[0141] As the dye, commercially available dyes and known dyes describedin publications (for example, Senryo Binran (Handbook of Dyes), compiledby Yuki Gosei Kagaku Kyokai (1970)) may be used. Specific examplesthereof include dyes such as azo dye, metal complex salt azo dye,pyrazolone azo dye, anthraquinone dye, phthalocyanine dye, carboniumdye, quinoneimine dye, methine dye and cyanine dye. Among these dyes,those which absorb infrared light or near infrared light are preferredbecause these are suitable for the use with a laser which emits infraredor near infrared light.

[0142] Examples of the dye which absorbs infrared or near infrared lightinclude cyanine dyes described in JP-A-58-125246, JP-A-59-84356,JP-A-60-78787, U.S. Pat. No. 4,973,572 and JP-A-10-268512, methine dyesdescribed in JP-A-58-173696, JP-A-58-181690 and JP-A-58-194595,naphthoquinone dyes described in JP-A-58-112793, JP-A-58-224793,JP-A-59-48187, JP-A-59-73996, JP-A-60-52940 and JP-A-60-63744,squarylium dyes described in JP-A-58-112792, cyanine dyes described inBritish Patent 434,875, cyanine dyes described in U.S. Pat. No.4,973,572, dyes described in JP-A-10-268512, and dyes represented by thefollowing formulae (I) and (II) described in U.S. Pat. No. 4,756,993:

[0143] [wherein R¹, R², R³, R⁴, R⁵ and R⁶ each represents a substitutedor unsubstituted alkyl group; Z¹ and Z² each represents a substituted orunsubstituted phenyl group or a naphthalene group; L represents asubstituted or unsubstituted methine group, the substituent is an alkylgroup having 8 or less carbon atoms, a halogen atom or an amino group orthe methine group may contain a cyclohexene or cyclopentene ring whichmay have a substituent and which is formed resulting from the combiningof substituents on two methine carbons with each other, and thesubstituent is an alkyl group having 6 or less carbon atoms or a halogenatom; X represents an anion; n is 1 or 2; and at least one of R¹, R²,R³, R⁴, R⁵, R⁶, Z¹ and Z² represents a substituent having an acidicgroup or an alkali metal salt or amine salt of an acidic group];

[0144] [wherein R¹¹ represents a substituted or unsubstituted alkylgroup, a substituted or unsubstituted aryl group or a substituted orunsubstituted heterocyclic group; R¹² and R¹⁵ each represents hydrogenatom or a group capable of substituting in place of hydrogen atom; R¹³and R¹⁴ each represents hydrogen atom, a halogen atom, a substituted orunsubstituted alkoxy group or a substituted or unsubstituted alkylgroup, provided that R¹³ and R¹⁴ are not simultaneously hydrogen atom;and R¹⁶ and R¹⁷ each represents a substituted or unsubstituted alkylgroup, a substituted or unsubstituted-aryl group, an acyl group or asulfonyl group, or R¹⁶ and R¹⁷ may form a nonmetallic 5- or 6-memberedring].

[0145] As the dye, the near infrared absorbing sensitizers described inU.S. Pat. No. 5,156,938 may also be suitably used. In particular,substituted arylbenzo(thio)pyrylium salts described in U.S. Pat. No.3,881,924, trimethine-thiapyrylium salts described in JP-A-57-142645(corresponding to U.S. Pat. No. 4,327,169), pyrylium-based compoundsdescribed in JP-A-58-181051, JP-A-58-220143, JP-A-59-41363,JP-A-59-84248, JP-59-84249, JP-A-59-146063 and JP-A-59-146061, cyaninedyes described in JP-A-59-216146, pentamethinethiapyrylium saltsdescribed in U.S. Pat. No. 4,283,475, pyrylium compounds described inJP-B-5-13514 and JP-B-5-19702, and Epolight III-178, Epolight III-130,Epolight and III-125 produced by Epolin are preferably used.

[0146] In the case of encapsulating the dye, in view of the synthesis, adye soluble in a solvent incapable of mixing with water, more preferablysoluble in ethyl acetate is preferred. Specific examples thereof includeoil-soluble cyanine dyes containing an alkyl chain having 4 or morecarbon atoms, oil-soluble phthalocyanine dyes and oil-solublepolymethine dyes.

[0147] Among these dyes, the water-soluble cyanine dye represented byformula (I) is particularly preferred.

[0148] Specific examples of the compound are set forth below.

[0149] The light-to-heat converting fine particulate metal is describedbelow. Many particulate metals are light-to-heat converting andself-exothermic.

[0150] Preferred examples of the fine particulate metal include fineparticles of Si, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Mo, Ag,Au, Pt, Pd, Rh, In, Sn, W, Te, Pb, Ge, Re and Sb as a single metal or analloy, and oxides and sulfides thereof.

[0151] Among these metals for constituting the fine particulate metal,preferred are metals having a melting point of 1,000° C. or less whereheat fusion readily takes place upon irradiation of light, and having anabsorption in the infrared, visible or ultraviolet region, such as Re,Sb, Te, Au, Ag, Cu, Ge, Pb and Sn.

[0152] Among these, more preferred are fine particles of metals having arelatively low melting point and exhibiting a relatively high absorbancefor the heat ray, such as Ag, Au, Cu, Sb, Ge and Pb. Particularlypreferred elements are Ag, Au and Cu.

[0153] The fine particulate metal may also consist of two or morelight-to-heat converting substances, which is obtained, for example, bymixing fine particles of a low melting point metal such as Re, Sb, Te,Au, Ag, Cu, Ge, Pb and Sn, and fine particles of a self-exothermic metalsuch as Ti, Cr, Fe, Co, Ni, W and Ge. A combination use of fine piecesof a metal seed which exhibits particularly large light absorption inthe form of fine piece, such as Ag, Pt and Pd, with other metal finepieces is also preferred.

[0154] The effect of the present invention can be brought out when thefine particle of metal as a single metal or an alloy is subjected to asurface hydrophilizing treatment. For the hydrophilization, a surfacetreatment with a hydrophilic compound having adsorptivity to theparticle, for example, with a surfactant or a substance having ahydrophilic group reacting with a constitution substance of theparticles, and a method of providing a protective colloidal hydrophilicpolymer coating may be used. A surface silicate treatment isparticularly preferred and for example, in the case of fine particulateiron, the surface can be fully hydrophilized by dipping the fineparticulate iron in an aqueous sodium silicate (3%) solution at 70° C.for 30 seconds. Other fine particulate metals can be surface-treatedwith silicate in the same manner.

[0155] The average particle size of these particles is 10 μm or less,preferably from 0.003 to 5 μm, more preferably from 0.01 to 3 μm. As theparticle size is smaller, the heat-fusion temperature decreases, inother words, the photosensitivity in the heat mode advantageouslyincreases, but the particles become difficult to disperse. If theparticle size exceeds 10 μm, the resolution of printed matter decreases.

[0156] In the present invention, when the light-to-heat convertingmaterial (infrared absorbent) is used, the amount added thereof is 1 wt% or more, preferably 2 wt % or more, more preferably 5 wt % or more,based on all solids content in the heat-sensitive layer (image recordinglayer). If the light-to-heat converting material content is less than 1wt %, the sensitivity decreases.

[0157] [Hydrophilic Resin]

[0158] The heat-sensitive layer of the lithographic printing plateprecursor of the present invention may contain a hydrophilic resin. Byadding a hydrophilic resin, not only good on-press developability can beattained but also the film strength of the heat-sensitive layer itselfincreases. The hydrophilic resin is preferably not three-dimensionallycrosslinked so as to ensure good on-press developability.

[0159] The hydrophilic resin preferably has a hydrophilic group such ashydroxyl, carboxyl, hydroxyethyl, hydroxypropyl, amino, aminoethyl,aminopropyl and carboxymethyl. Specific examples of the hydrophilicresin include gum arabic, casein, gelatin, starch derivatives,carboxymethyl cellulose and Na salt thereof, cellulose acetate, sodiumalginate, vinyl acetate-maleic acid copolymers, styrene-maleic acidcopolymers, polyacrylic acids and salts thereof, polymethacrylic acidsand salts thereof, homopolymers and copolymers of hydroxyethylmethacrylate, homopolymers and copolymers of hydroxyethyl acrylate,homopolymers and copolymers of hydroxypropyl methacrylate, homopolymersand copolymers of hydroxypropyl acrylate, homopolymers and copolymers ofhydroxybutyl methacrylate, homopolymers and copolymers of hydroxybutylacrylate, polyethylene glycols, hydroxypropylene polymers, polyvinylalcohols, hydrolyzed polyvinyl acetate having a hydrolysis degree of atleast 60 wt %, preferably at least 80 wt %, polyvinyl formal, polyvinylbutyral, polyvinyl pyrrolidone, homopolymers and copolymers ofacrylamide, homopolymers and copolymers of methacrylamide, homopolymersand copolymers of N-methylolacrylamide, and homopolymers and copolymersof 2-acrylamide-2-methylpropanesulfonic acid and salts thereof.

[0160] The amount of the hydrophilic resin added to the heat-sensitivelayer is preferably from 2 to 40%, more preferably from 3 to 30%. If theamount added is less than 2%, the coating becomes low in the strength,whereas if it exceeds 40%, the press life deteriorates though theon-press developability is improved.

[0161] [Compound which Initiates or Accelerates Reaction]

[0162] The heat-sensitive layer of the lithographic printing plateprecursor of the present invention uses the above-described fineparticulate polymer having a reactive group, or the microcapsulecontaining a compound having a thermally reactive group, therefore, ifdesired, a compound which initiates or accelerates the reaction of thepolymer or microcapsule may be added. Examples thereof include compoundswhich generate radical or cation by heat, such as lophine dimers,trihalomethyl compounds, peroxides, azo compounds, onium saltscontaining diazonium salt or diphenyl iodonium salt, acylphosphine andimidosulfonate.

[0163] This compound may be added to the heat-sensitive layer in therange from 1 to 20 wt %, preferably from 3 to 10 wt %. If the amountadded exceeds this range, the on-press developability changes for theworse, whereas if it is less than the range, the effect of initiating oraccelerating the reaction decreases and the press life properties aredeteriorated.

[0164] In the case of using a microcapsule, a compound which initiatesor accelerates the reaction is preferably incorporated into the insideof microcapsule so as to attain efficient progress of the reaction. Byincorporating the compound into the inside of the microcapsule, apreviously well mixed state with the compound having a thermallyreactive group can be provided and upon irradiation of a laser, thereaction can proceed along with the bleeding out or release of theencapsulated materials, whereby the lithographic printing plateprecursor of the present invention can be more improved in the presslife.

[0165] [(Low Molecular) Compound Which Reacts with Fine ParticulatePolymer Capable of Combining or Incapable of Combining by Heat Used forImage Formation]

[0166] The heat-sensitive layer of the lithographic printing plateprecursor of the present invention may further contain a (low molecular)compound having a functional group capable of reacting with the reactivegroup in the fine particulate polymer and a protective group thereof.The amount of this compound added is preferably from 5 to 40 wt %, morepreferably from 5 to 20 wt %, based on the heat-sensitive layer. If theamount added thereof is less than this range, the effect by thecrosslinking is not brought out and insufficient press life results,whereas if it exceeds the above-described range, the on-pressdevelopability changes for the worse after the aging. The compound whichcan be used is described below.

[0167] The (low molecular) compound includes compounds having anunsaturated group. The compound having an unsaturated group is a radicalpolymerizable compound having at least one ethylenically unsaturateddouble bond and the compound is selected from the compounds having atleast one, preferably two or more ethylenically unsaturated terminalbonds. Such compounds are widely known in this industrial field andthose known compounds all can be used in the present invention withoutany limit. This compound has, a chemical form of, for example, monomer,prepolymer, more specifically, dimer, trimer or oligomer, a mixturethereof or a copolymer thereof. Examples of the monomer and itscopolymer include unsaturated carboxylic acids (e.g., acrylic acid,methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleicacid), and esters and amides thereof. Among these, preferred are estersof an unsaturated carboxylic acid with an aliphatic polyhydric alcoholcompound, and amides of an unsaturated carboxylic acid with an aliphaticpolyhydric amine compound. Also, addition reaction products of anunsaturated carboxylic acid ester or amide having a nucleophilicsubstituent such as hydroxyl group, amino group or mercapto group with amonofunctional or polyfunctional isocyanate or epoxy, and dehydrationcondensation reaction products with a monofunctional or polyfunctionalcarboxylic acid may be suitably used. Furthermore, addition reactionproducts of an unsaturated carboxylic acid ester or amide having anelectrophilic substituent such as isocyanate group or epoxy group with amonofunctional or polyfunctional alcohol, amine or thiol, andsubstitution reaction products of an unsaturated carboxylic acid esteror amide having an eliminating substituent such as halogen group ortosyloxy group with a monofunctional or polyfunctional alcohol, amine orthiol may also be suitably used. These compounds but where theunsaturated carboxylic acid is replaced by an unsaturated phosphonicacid, styrene or the like, may also be used.

[0168] Specific examples of the radical polymerizable compound which isan ester of an aliphatic polyhydric alcohol compound with an unsaturatedcarboxylic acid include acrylic acid esters such as ethylene glycoldiacrylate, triethylene glycol diacrylate, 1,3-butanediol diacrylate,tetramethylene glycol diacrylate, propylene glycol diacrylate, neopentylglycol diacrylate, trimethylolpropane triacrylate, trimethylolpropanetri-(acryloyloxypropyl) ether, trimethylolethane triacrylate, hexanedioldiacrylate, 1,4-cyclohexanediol diacrylate, tetraethylene glycoldiacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate,pentaerythritol tetraacrylate, dipentaerythritol diacrylate,dipentaerythritol hexaacrylate, sorbitol triacrylate, sorbitoltetraacrylate, sorbitol pentaacrylate, sorbitol hexaacrylate,tri-(acryloyloxyethyl)isocyanurate and polyester acrylate oligomer;

[0169] methacrylic acid esters such as tetramethylene glycoldimethacrylate, triethylene glycol dimethacrylate, neopentyl glycoldimethacrylate, trimethylolpropane trimethacrylate, trimethylolethanetrimethacrylate, ethylene glycol dimethacrylate, 1,3-butanedioldimethacrylate, hexanediol dimethacrylate, pentaerythritoldimethacrylate, pentaerythritol trimethacrylate, pentaerythritoltetramethacrylate, dipentaerythritol dimethacrylate, dipentaerythritolhexamethacrylate, sorbitol trimethacrylate, sorbitol tetramethacrylate,bis[p-(3-methacryloxy-2-hydroxypropoxy)phenyl]dimethylmethane andbis[p-(methacryloxyethoxy)phenyl]dimethylmethane;

[0170] itaconic acid esters such as ethylene glycol diitaconate,propylene glycol diitaconate, 1,3-butanediol diitaconate, 1,4-butanedioldiitaconate, tetramethylene glycol diitaconate, pentaerythritoldiitaconate and sorbitol tetraitaconate;

[0171] crotonic acid esters such as ethylene glycol dicrotonate,tetramethylene glycol dicrotonate, pentaerythritol dicrotonate andsorbitol tetradicrotonate;

[0172] isocrotonic acid esters such as ethylene glycol diisocrotonate,pentaerythritol diisocrotonate and sorbitol tetraisocrotonate; and

[0173] maleic acid esters such as ethylene glycol dimaleate, triethyleneglycol dimaleate, pentaerythritol dimaleate and sorbitol tetramaleate.

[0174] Other examples of the ester include aliphatic alcohol-basedesters described in JP-B-46-27926, JP-B-51-47334 and JP-A-57-196231,those having an aromatic skeleton described in JP-A-59-5240,JP-A-59-5241 and JP-A-2-226149, and those containing an amino groupdescribed in JP-A-1-165613.

[0175] Specific examples of the amide monomer of an aliphatic polyhydricamine compound with an unsaturated carboxylic acid includemethylenebis-acrylamide, methylenebis-methacrylamide,1,6-hexamethylenebis-acrylamide, 1,6-hexamethylenebis-methacrylamide,diethylenetriaminetris-acrylamide, xylylenebisacrylamide andxylylenebis-methacrylamide.

[0176] Other preferred examples of the amide-type monomer include thosehaving a cyclohexylene structure described in JP-B-54-21726.

[0177] A urethane-based addition polymerizable compound produced byusing an addition reaction of isocyanate and a hydroxyl group is alsosuitably used and specific examples thereof include vinyl urethanecompounds having two or more polymerizable vinyl groups within onemolecule described in JP-B-48-41708, which are obtained by adding avinyl monomer having a hydroxyl group represented by the followingformula (A) to a polyisocyanate compound having two or more isocyanategroups within one molecule:

CH₂═C(R₄₁)COOCH₂CH(R₄₂)OH  (A)

[0178] (wherein R₄₁, and R₄₂ each represents H or CH₃)

[0179] Also, urethane acrylates described in JP-A-51-37193, JP-B-2-32293and JP-B-2-16765, and urethane compounds having an ethylene oxide-typeskeleton described in JP-B-58-49860, JP-B-56-17654, JP-B-62-39417 andJP-B-62-39418 are also suitably used.

[0180] Furthermore, radical polymerizable compounds having an amino orsulfide structure within the molecule described in JP-A-63-277653,JP-A-63-260909 and JP-A-1-105238 may be used.

[0181] Other examples include polyfunctional acrylates and methacrylatessuch as polyester acrylates described in JP-A-48-64183, JP-B-49-43191and JP-B-52-30490 and epoxy acrylates obtained by reacting an epoxyresin with a (meth)acrylic acid. In addition, specific unsaturatedcompounds described in JP-B-46-43946, JP-B-1-40337 and JP-B-1-40336, andvinyl phosphonic acid-based compounds described in JP-A-2-25493 may beused. In some cases, structures containing a perfluoroalkyl groupdescribed in JP-A-61-22048 are suitably used. Furthermore, thosedescribed as a photocurable monomer or oligomer in Nippon SecchakuKyokaishi (Journal of Japan Adhesive Society), Vol. 20, No. 7, pp.300-308 (1984) may also be used.

[0182] Preferred examples of the epoxy compound include glycerinpolyglycidyl ether, polyethylene glycol diglycidyl ether, polypropylenediglycidyl ether, trimethylol propane polyglycidyl ether, sorbitolpolyglycidyl ether, bisphenols, polyphenols and hydrogenated productsthereof, namely, polyglycidyl ether forms thereof.

[0183] Preferred examples of the compound having an isocyanate includetolylene diisocyanate, diphenylmethane diisocyanate, polymethylenepolyphenyl polyisocyanate, xylylene diisocyanate, naphthalenediisocyanate, cyclohexane phenylene diisocyanate, isophoronediisocyanate, hexamethylene diisocyanate, cyclohexyl diisocyanate andblocked compounds thereof with an alcohol or an amine.

[0184] Preferred examples of the amine compound include ethylenediamine,diethylenetriamine, triethylenetetramine, hexamethylenediamine,propylenediamine and polyethyleneimine.

[0185] Preferred examples of the compound having a hydroxyl groupinclude compounds having a terminal methylol, polyhydric alcohols suchas pentaerythritol, bisphenols and polyphenols.

[0186] Preferred examples of the compound having a carboxyl groupinclude aromatic polyhydric carboxylic acids such as pyromellitic acid,trimellitic acid and phathalic acid, and aliphatic polyhydric carboxylicacids such as adipic acid.

[0187] Preferred examples of the acid anhydride include pyromelliticacid anhydride and benzophenonetetracarboxylic acid anhydride.

[0188] [Low Molecular Compound Which Reacts with Compound HavingThermally Reactive Group Contained in Microcapsule]

[0189] The heat-sensitive layer of the lithographic printing plateprecursor of the present invention may further contain a low molecularcompound having a functional group capable of reacting with a compoundhaving a thermally reactive group contained in the microcapsule, by heatused for the image formation and a protective group thereof. The amountof this compound added is preferably from 5 to 40 wt %, more preferablyfrom 5 to 20 wt %, based on the heat-sensitive layer. If the amountadded is less than this range, the effect by the crosslinking is notbrought out and insufficient press life results, whereas if it exceedsthe above-described range, the on-press developability changes for theworse after the aging. Specific examples of this compound include thosedescribed above as the specific examples of the compound having athermally reactive group contained in the microcapsule.

[0190] [Other Additives]

[0191] In the present invention, other than those described above,various compounds may further be added, if desired. For example, a dyehaving a large absorption in the visible light region may be used as acolorant of the image. Specific examples thereof include Oil Yellow#101, Oil Yellow #103, Oil Pink #312, Oil Green BG, Oil Blue BOS, OilBlue #603, Oil Black BY, Oil Black BS, Oil Black T-505 (all are producedby Orient Kagaku Kogyo K.K.), Victoria Pure Blue, Crystal Violet(CI42555), Methyl Violet (CI42535), Ethyl Violet, Rhodamine B(CI145170B), Malachite Green (CI42000), Methylene Blue (CI52015), anddyes described in JP-A-62-293247. Also, pigments such asphthalocyanine-based pigments, azo-based pigments, carbon black andtitanium oxide may be suitably used.

[0192] The colorant is preferably added so as to provide cleardistinction between the image area and the non-image area after theimage formation. The amount of the colorant added is from 0.01 to 10 wt% based on all solids content of the coating solution for theheat-sensitive layer.

[0193] In the present invention, a slight amount of athermopolymerization inhibitor is preferably added so as to inhibitunnecessary thermopolymerization of the compound having an ethylenicallyunsaturated double bond capable of radical polymerization duringpreparation or storage of the coating composition for the heat-sensitivelayer. Suitable examples of the thermopolymerization inhibitor includehydroquinone, p-methoxyphenol, di-t-butyl-p-cresol, pyrogallol, t-butylcatechol, benzoquinone, 4,440 -thiobis(3-methyl-6-t-butylphenol), 2,240-methylenebis(4-methyl-6-t-butylphenol) andN-nitroso-N-phenylhydroxylamine aluminum salt. The amount of thethermopolymerization inhibitor added is preferably from about 0.01 wt %to about 5 wt % based on the weight of the entire composition. Ifdesired, a higher fatty acid derivative such as behenic acid or behenicacid amide may be added and allowed to localize on the surface of theheat-sensitive layer in the process of drying after the coating so as toprevent polymerization inhibition by oxygen. The amount of the higherfatty acid derivative added is preferably from about 0.1 wt % to about10 wt % based on the entire composition.

[0194] The composition for the heat-sensitive layer of the presentinvention may contain a nonionic surfactant described in JP-A-62-251740and JP-A-3-208514 or an amphoteric surfactant described inJP-A-59-121044 and JP-A-4-13149 so as to broaden the processingstability against development conditions.

[0195] Specific examples of the nonionic surfactant include sorbitantristearate, sorbitan monopalmitate, sorbitan trioleate, stearic acidmonoglyceride and polyoxyethylenenonylphenyl ether.

[0196] Specific examples of the amphoteric surfactant include alkyldi(aminoethyl)glycine, alkylpolyaminoethyl glycine hydrochloride,2-alkyl-N-carboxyethyl-N-hydroxyethyl-imidazolinium betaine andN-tetradecyl-N,N-betaine type (for example, AMORGEN K, trade name,produced by Daiichi Kogyo K.K.).

[0197] The ratio of the nonionic surfactant or amphoteric surfactantoccupying in the coating composition for the heat-sensitive layer ispreferably from 0.05 to 15 wt %, more preferably from 0.1 to 5 wt %.

[0198] The coating composition for the heat-sensitive layer of thepresent invention may further contain, if desired, a plasticizer forimparting flexibility to the coated film. Examples thereof includepolyethylene glycol, tributyl citrate, diethyl phthalate, dibutylphthalate, dihexyl phthalate, dioctyl phthalate, tricresyl phosphate,tributyl phosphate, trioctyl phosphate and tetrahydrofurfuryl oleate.

[0199] The lithographic printing plate precursor of the presentinvention may be produced by dissolving the above-described componentsnecessary for the coating solution for the heat-sensitive layer in asolvent and coating the obtained solution on an appropriate support.Examples of the solvent used here include ethylene dichloride,cyclohexanone, methyl ethyl ketone, methanol, ethanol, propanol,ethylene glycol monomethyl ether, 1-methoxy-2-propanol, 2-methoxyethylacetate, 1-methoxy-propyl acetate, dimethoxyethane, methyl lactate,ethyl lactate, N,N-dimethylacetamide, N,N-dimethylformamide,tetramethylurea, N-methylpyrrolidone, dimethylsulfoxide, sulfolane,γ-butyl lactone, toluene and water, however, the present invention isnot limited thereto. These solvents are used individually or incombination. The concentration of the above-described components (theentire solids content containing additives) in the solvent is preferablyfrom 1 to 50 wt %.

[0200] The amount (solids content) coated of the heat-sensitive layerobtained on the support after the coating and drying varies depending onthe use, however, in the case of a lithographic printing plate precursorin general, it is preferably from 0.5 to 5.0 g/m². The coating solutionmay be coated by various methods such as bar coater coating, rotationcoating, spray coating, curtain coating, dip coating, air knife coating,blade coating and roll coating. As the amount coated is larger, theapparent sensitivity becomes higher, however, the heat-sensitive layerdeteriorates in the properties of the coating necessary for the functionof recording image.

[0201] The coating solution for the heat-sensitive layer according tothe present invention may contain a surfactant so as to improve thecoatability, such as a fluorine-containing surfactant described, forexample, in JP-A-62-170950. The amount of the surfactant added ispreferably from 0.01 to 1 wt %, more preferably from 0.05 to 0.5 wt %,based on the entire solids content of materials in the heat-sensitivelayer.

[0202] [Overcoat Layer]

[0203] In the lithographic printing plate precursor of the presentinvention, a water-soluble overcoat layer may be provided on theheat-sensitive layer so as to prevent staining on the surface of theheat-sensitive layer due to lipophilic substances. The water-solubleovercoat layer for use in the present invention is a layer which can beeasily removed at the printing, and contains a resin selected fromwater-soluble organic polymer compounds. The water-soluble organicpolymer compound provides, when coated and dried, a coating having afilm-forming ability. Specific examples thereof include polyvinylacetate (having, however, a hydrolysis ratio of 65% or more),polyacrylic acid and alkali metal and amine salts thereof, polyacrylicacid copolymers and alkali metal and amine salts thereof,polymethacrylic acid and alkali metal and amine salts thereof,polymethacrylic acid copolymers and alkali metal and amine saltsthereof, polyacrylamide and copolymers thereof, polyhydroxyethylacrylate, polyvinylpyrrolidone and copolymers thereof, polyvinyl methylether, polyvinyl methyl ether/maleic acid anhydride copolymers,poly-2-acrylamide-2-methyl-1-propanesulfonic acid and alkali metal andamine salts thereof, poly-2-acrylamide-2-methyl-1-propanesulfonic acidcopolymers and alkali metal and amine salts thereof, gum arabic,cellulose derivatives (e.g., carboxymethyl cellulose, carboxyethylcellulose, methyl cellulose) and modifications thereof, white dextrin,pullulan and enzymolysis etherified dextrin. According to the purpose,these resins can be used in combination of two or more thereof.

[0204] The overcoat layer may contain the above-described water-solublelight-to-heat converting agent. The overcoat layer may further contain,in the case of coating as an aqueous solution, a nonionic surfactantsuch as polyoxyethylenenonylphenyl ether and polyoxyethylenedodecylether, so as to ensure uniformity of the coating.

[0205] The overcoat layer preferably has a dry coated amount of 0.1 to2.0 g/m². If the dry coated amount is less than this range, staining byattaching of a finger print may arise, whereas if it exceeds theabove-described range, the on-press developability deteriorates.

[0206] [Support]

[0207] In the lithographic printing plate precursor of the presentinvention, the hydrophilic support where the heat-sensitive layer can becoated is a plate-like material having good dimensional stability andexamples thereof include paper, paper laminated with plastic (e.g.,polyethylene, polypropylene, polystyrene), metal plates (e.g., aluminum,zinc, copper), plastic film (e.g., cellulose diacetate, cellulosetriacetate, cellulose propionate, cellulose butyrate, cellulose butyrateacetate, cellulose nitrate, polyethylene terephthalate, polyethylene,polystyrene, polypropylene, polycarbonate, polyvinyl acetal), and paperor plastic film having laminated or deposited thereon theabove-described metal. Among these, a polyester film or an aluminumplate is preferred.

[0208] The support for use in the lithographic printing plate precursorof the present invention is preferably an aluminum plate which islightweight and excellent in the surface-treating property, workabilityand corrosion resistance. Examples of the aluminum material used to thispurpose include JIS 1050 material, JIS 1100 material, JIS 1070 material,Al—Mg system alloy, Al—Mn system alloy, Al—Mn—Mg system alloy, Al—Zrsystem alloy and Al—Mg—Si system alloy.

[0209] Well-known techniques related to the aluminum material which canbe used for the support, are enumerated below.

[0210] (1) With respect to JIS 1050 material, the following techniquesare disclosed: JP-A-59-153861, JP-A-61-51395, JP-A-62-146694,JP-A-60-215725, JP-A-60-215726, JP-A-60-215727, JP-A-60-215728,JP-A-61-272357, JP-A-58-11759, JP-A-58-42493, JP-A-58-221254,JP-A-62-148295, JP-A-4-254545, JP-A-4-165041, JP-A-3-689393,JP-A-3-234594, JP-B-1-47545, JP-A-62-140894, JP-B-1-35910 andJP-B-55-28874.

[0211] (2) With respect to JIS 1070 material, the following techniquesare disclosed:

[0212] JP-A-7-81264, JP-A-7-305133, JP-A-8-49034, JP-A-8-73974,JP-A-8-108659 and JP-A-8-92679.

[0213] (3) With respect to the Al—Mg system alloy, the followingtechniques are disclosed:

[0214] JP-B-62-5080, JP-B-63-60823, JP-B-3-61753, JP-A-60-203496,JP-A-60-203497, JP-B-3-11635, JP-A-61-274993, JP-A-62-23794,JP-A-63-47347, JP-A-63-47348, JP-A-63-47349, JP-A-64-61293,JP-A-63-135294, JP-A-63-87288, JP-B-4-73392, JP-B-7-100844,JP-A-62-149856, JP-B-4-73394, JP-A-62-182291, JP-B-5-76530,JP-A-63-30294, JP-B-6-37116, JP-A-2-215599 and JP-A-61-201747.

[0215] (4) With respect to the Al—Mn system alloy, the followingtechniques are disclosed:

[0216] JP-A-60-230951, JP-A-1-306288, JP-A-2-293189, JP-B-54-42284,JP-B-4-19290, JP-B-4-19291, JP-B-4-19292, JP-A-61-35995, JP-A-64-51992,U.S. Pat. Nos. 5,009,722 and 5,028,276 and JP-A-4-226394.

[0217] (5) With respect to the Al—Mn—Mg system alloy, the followingtechniques are disclosed:

[0218] JP-A-62-86143, JP-A-3-222796, JP-B-63-60824, JP-A-60-63346,JP-A-60-63347, EP223737, JP-A-1-283350, U.S. Pat. No. 4,818,300 andBritish Patent 1,222,777.

[0219] (6) With respect to the Al—Zr system alloy, the followingtechniques are disclosed:

[0220] JP-A-63-15978, JP-A-61-51395, JP-A-63-143234 and JP-A-63-143235.

[0221] (7) With respect to the Al—Mg—Si system alloy, British Patent1,421,710 is known.

[0222] With respect to the production method of the aluminum plate forsupport, the following methods may be used.

[0223] A molten metal of aluminum alloy containing the above-describedcomponents and alloy component ratio is subjected to a cleaningtreatment by an ordinary method and then cast. In the cleaningtreatment, for removing unnecessary gas such as a hydrogen gas in themolten metal, a flux treatment, a degassing treatment using Ar gas or Clgas, filtering using a so-called rigid media filter such as ceramic tubefilter and ceramic form filter, a filter using alumina flake or aluminaball as the filter medium, or a glass cloth filter, or a treatment usinga combination of degassing and filtering, is performed. This cleaningtreatment is preferably performed so as to prevent occurrence of defectsdue to foreign matters in the molten metal, such as nonmetallicinclusion or oxide, or defects due to gas dissolved in the molten metal.

[0224] The techniques on filtering of the molten metal are known inJP-A-6-57342, JP-A-3-162530, JP-A-5-140659, JP-A-4-231425,JP-A-4-276031, JP-A-5-311261 and JP-A-6-136466.

[0225] The techniques on degassing of the molten metal are known inJP-A-5-51659, JP-A-5-51660, JP-U-A-5-49148 and JP-A-7-40017.

[0226] The molten metal thus subjected to a cleaning treatment is thencast. The casting method includes a method using a fixed mold,represented by DC casting, and a method using a driving mold,represented by continuous casting.

[0227] In the case of using DC casting, the molten metal is solidifiedat a cooling rate of 1 to 300° C./sec. If the cooling rate is less than1° C./sec., a large number of coarse intermetallic compounds are formed.

[0228] Examples of the continuous casting which is used in industryinclude a Hunter method, a method using a cold roll, represented by 3Cmethod, a Hazelett method, and a method using cooling belt or coolingblock, represented by Alusuisse Caster II. In the case of usingcontinuous casting, the molten metal is solidified at a cooling rate of100 to 1,000° C./sec. In general, the cooling rate is high as comparedwith DC casting and therefore, the solid solubility of the alloycomponents based on the aluminum matrix can be elevated. The continuouscasting method is disclosed by the present inventors in JP-A-3-79798,JP-A-5-201166, JP-A-5-156414, JP-A-6-262203, JP-A-6-122949,JP-A-6-210406 and JP-A-6-262308.

[0229] In the case of performing DC casting, an ingot having a platethickness of 300 to 800 nm is produced. This ingot is scalped by anordinary method to cut from 1 to 30 mm, preferably from 1 to 10 mm, ofthe surface layer. Thereafter, the plate is soaked, if desired. In thesoaking treatment, a heat treatment is performed at 450 to 620° C. for 1to 48 hours so as not to cause coarsening of the intermetallic compound.If the treating time is less than 1 hour, the effect attained by thesoaking treatment is insufficient. Subsequently, the aluminum plate ishot-rolled and then cold-rolled to obtain an aluminum rolled plate. Thetemperature at the initiation of hot rolling is in the range from 350 to500° C. Before, after or during the cold rolling, intermediate annealingmay be applied. The intermediate annealing is performed under heatingconditions of, in the case of using a batch-system annealing furnace,280 to 600° C. for 2 to 20 hours, preferably 350 to 500° C. for 2 to 10hours, or in the case of using a continues annealing furnace, 400 to600° C. for 360 seconds or less, preferably 450 to 550° C. for 120seconds or less. By using a continuous annealing furnace and elevatingthe heating temperature at a rate of 10° C./sec or more, the crystalstructure may be made fine.

[0230] The Al plate finished to a predetermined thickness of 0.1 to 0.5mm through the above-described steps may be improved in the planeness bya sizing apparatus such as roller leveler and tension leveler. Theimprovement of planeness may be performed after cutting the plate into asheet form but in order to elevating the productivity, the improvementof planeness is preferably performed while the plate is in a continuouscoil state. For the working to a predetermined plate width, the Al plateis usually passed through slitter line. On the edge face cut by theslitter, one or both of sheared surface and ruptured surface aregenerated at the cutting by the slitter blade.

[0231] The plate thickness accuracy is suitably within ±10 μm,preferably within ±6 μm, over the entire coil length. The platethickness difference in the width direction is suitably within 6 μm,preferably within 3 μm. The plate width accuracy is suitably within ±1.0mm, preferably within ±0.5 mm. The surface roughness of the Al plate isreadily affected by the surface roughness of the roller, but the Alplate is preferably finished to finally have a center line (average)surface roughness (Ra) of approximately from 0.1 to 1.0 μm. If the Ra isexcessively large, the original roughness of Al, namely, rolled streakstransferred from the roller, is viewed through the heat-sensitive layerafter a lithographic printing plate is completed by the rougheningtreatment and coating of the heat-sensitive layer and this is notpreferred in view of appearance. On the other hand, if Ra is less than0.1 μm, the surface of the roller must be finished to have excessivelylow roughness and this is industrially disadvantageous.

[0232] In order to prevent generation of scratches due to frictionbetween Al plates, a thin oil film may be provided on the surface of theAl plate. For the oil film, a volatile material or an nonvolatilematerial is appropriately used according to the purpose. If the oilamount is excessively large, slipping failure may occur in theproduction line, whereas if the oil amount is nil, troubles such asgeneration of scratches take place during the transportation of coils.Accordingly, the amount is suitably from 3 to 100 mg/m². The upper limitthereof is preferably 50 mg/m² or less, more preferably 10 mg/m² orless. With respect to the cold rolling, details are disclosed inJP-A-6-210308.

[0233] In the case of performing continuous casting, for example, when acooling roller by the Hunter method is used, a cast plate having athickness of 1 to 10 mm can be directly and continuously cast and rolledand the hot-rolling step can be advantageously dispensed with. When acooling roller by the Hazelett method is used, a cast plate having athickness of 10 to 50 mm can be cast and in general, by disposing ahot-rolling roller immediately after the casting and continuouslyrolling the plate, a continuously cast and rolled plate having athickness of 1 to 10 mm can be obtained. These continuously cast androlled plates are, in the same manner as described in the case of DCcasting, subjected to cold rolling, intermediate annealing, improvementof planeness, slitting and the like and finished to a plate thickness of0.1 to 0.5 mm. The intermediate annealing conditions and cold rollingconditions in the case of using a continuous casting method aredescribed in JP-A-6-220593, JP-A-6-210308, JP-A-7-54111 andJP-A-8-92709.

[0234] The thus-produced Al plate is subjected to a surface treatmentsuch as roughening of the surface, and then a heat-sensitive layer iscoated thereon, thereby producing a lithographic printing plateprecursor. The surface roughening treatment is performed usingmechanical roughening, chemical roughening and electrochemicalroughening individually or in combination. Furthermore, it is preferredto perform an anodization treatment to ensure resistance againstscratches on the surface or to perform a treatment for increasing thehydrophilicity.

[0235] The surface treatment of the support is described below.

[0236] In advance of the surface roughening, the aluminum plate may besubjected, if desired, to a degreasing treatment, for example, with asurfactant, an organic solvent or an alkaline aqueous solution, so as toremove the rolling oil on the surface. In the case of using an alkalineaqueous solution, a treatment with an acidic solution may be performedto effect neutralization and desmutting.

[0237] Thereafter, a so-called graining treatment is performed, wherethe support surface is roughened so as to attain good adhesion betweenthe support and the heat-sensitive layer and at the same time to impartwater receptivity to the non-image area. To speak specifically, themeans for this graining treatment includes a mechanical graining methodsuch as sand blast, ball graining, wire graining, brush graining bynylon brush and abrasive/water slurry, and horning of collidingabrasive/water slurry to the surface under high pressure, and a chemicalgraining method of roughening the surface with an etching agentcomprising an alkali, an acid or a mixture thereof. In addition, anelectrochemical graining method described in British Patent 896,563,JP-A-53-67507, JP-A-54-146234 and JP-B-48-28123, a method using acombination of mechanical graining and an electrochemical grainingdescribed in JP-A-53-123204 and JP-A-54-63902, and a method using acombination of mechanical graining and chemical graining with asaturated aqueous solution containing mineral acid and aluminum saltdescribed in JP-A-56-55261, are known. Furthermore, the surface may beroughened by a method of adhering granular materials using an adhesiveor means having the adhesive effect to the support material or bypress-contacting a continuous belt or roller having fine asperities tothe support material and transferring the asperities.

[0238] A plurality of these surface roughening methods may be used incombination, and the order, repetition number and the like can be freelyselected. In the case of using a plurality of surface rougheningtreatments in combination, a chemical treatment with an acid or alkaliaqueous solution may be interposed between respective treatments so asto ensure uniform treatment of the subsequent surface rougheningtreatment. Specific examples of the acid or alkali aqueous solutioninclude an aqueous solution of acid such as hydrofluoric acid,fluorozirconate, phosphoric acid, sulfuric acid, hydrochloric acid andnitric acid, and an aqueous solution of alkali such as sodium hydroxide,sodium silicate and sodium carbonate. These acid or alkali aqueoussolutions can be used individually or in combination of two or morethereof. In general, the chemical treatment is performed using a 0.05 to40 wt % aqueous solution of the above-described acid or alkali at aliquid temperature of 40 to 100° C. for 5 to 300 seconds.

[0239] On the surface of the support subjected to the above-describedsurface roughening treatment, namely, graining, smuts are generated,therefore, for removing the smuts, the support is in general preferablywashed with water or subjected to a treatment such as alkali etching.Examples of this treatment include alkali etching described inJP-B-48-28123 and desmutting with sulfuric acid described inJP-A-53-12739.

[0240] In the case of the aluminum support for use in the presentinvention, after the above-described pretreatment is applied, ananodized oxide film is usually formed on the support by anodization soas to improve abrasion resistance, chemical resistance and waterreceptivity.

[0241] The electrolyte for use in the anodization treatment of thealuminum plate may be any as long as it forms a porous anodized oxidefilm. In general, sulfuric acid, phosphoric acid, oxalic acid, chromicacid or a mixed acid thereof is used. The concentration of theelectrolyte is appropriately determined depending on the kind of theelectrolyte. The conditions for anodization treatment vary depending onthe electrolyte used and cannot be indiscriminately specified, however,the conditions in general are suitably such that the concentration ofelectrolyte is from 1 to 80% solution, the liquid temperature is from 5to 70° C., the current density is from 5 to 60 A/dM², the voltage isfrom 1 to 100 V, and the electrolysis time is from 10 seconds to 5minutes. The amount of the anodized film is suitably 1.0 g/m² or more,preferably from 2.0 to 6.0 g/m². If the anodized film is less than 1.0g/m², insufficient press life results or the non-image area of thelithographic printing plate is readily scratched and so-called “scratchstaining” due to attachment of ink to the scratched portion is liable tooccur at the printing.

[0242] The anodization treatment is applied to the surface of thesupport for a lithographic printing plate precursor, which surface isused for printing, but by extending the electric force line over theback surface, an anodized film of 0.01 to 3 g/m² is generally formed onthe back surface. Also, an anodization treatment in an alkali aqueoussolution (for example, an aqueous solution containing a few % of sodiumhydroxide) or a molten salt, or an anodization treatment of forming anon-porous anodized film using, for example, an aqueous ammon boratesolution may be performed.

[0243] Before the anodization, a hydrous oxide film described inJP-A-4-148991 and JP-A-4-87896 may be formed or a treatment in metalsilicate solution described in JP-A-63-56497 and JP-A-63-67295, ahydrous oxide film-forming treatment, or a chemical formationfilm-forming treatment described in JP-A-56-144195 may be performed.

[0244] After the anodization treatment, the aluminum support for use inthe lithographic printing plate precursor of the present invention maybe treated with an organic acid or a salt thereof, or use the organicacid or a salt thereof as an undercoat layer for the coating of theheat-sensitive layer. Examples of the organic acid or a salt thereofinclude organocarboxylic acid, organophosphonic acid, organosulfonicacid and salts thereof, with organocarboxylic acid and salts thereofbeing preferred. Examples of the organocarboxylic acid include aliphaticmonocarboxylic acids such as formic acid, acetic acid, propionic acid,butyric acid, lauric acid, palmitic acid and stearic acid; unsaturatedaliphatic monocarboxylic acids such as oleic acid and linoleic acid;aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipicacid and maleic acid; oxycarboxylic acids such as lactic acid, gluconicacid, malic acid, tartaric acid and citric acid; aromatic carboxylicacids such as benzoic acid, mandelic acid, salicylic acid and phthalicacid; and metal salts belonging to Groups Ia, IIb, IIIb, IVa, IVb andVIII, and ammonium salts. Among these organic carboxylates, preferredare the metal salts and ammonium salts of formic acid, acetic acid,butyric acid, propionic acid, lauric acid, oleic acid, succinic acid andbenzoic acid. These compounds may be used individually or in combinationof two or more thereof.

[0245] This compound is preferably dissolved in an alcohol to have aconcentration of 0.001 to 10 wt %, more preferably from 0.01 to 1.0 wt%. In the treatment, the support is dipped in the treating solutionunder the conditions such that the temperature is from 25 to 95° C.,preferably from 50 to 95° C., the pH is from 1 to 13, preferably from 2to 10, for from 10 seconds to 20 minutes, preferably from 10 seconds to3 minutes, or the treating solution is coated on the support.

[0246] Also, after the anodization, the support may be treated with asolution containing the following compound or may use the compound as anundercoat layer for the coating of the heat-sensitive layer. Examples ofthe compound which can be suitably used include organo-phosphonic acidssuch as phenylphosphonic acid, naphthyl-phosphonic acid, alkylphosphonicacid, glycerophosphonic acid, methylenediphosphonic acid andethylenediphosphonic acid, which may have a substituent;organophosphoric acids such as phenylphosphoric acid, naphthylphosphoricacid, alkylphosphoric acid and glycerophosphoric acid, which may have asubstituent; organophosphinic acids such as phenylphosphinic acid,naphthylphosphinic acid, alkylphosphinic acid and glycerophosphinicacid, which may have a substituent; amino acids such as glycine,β-alanine, valine, serine, threonine, aspartic acid, glutamic acid,arginine, lysine, tryptophan, parahydroxyphenyl glycine, dihydroxyethylglycine and anthranilic acid; aminosulfonic acids such as sulfamic acidand cyclohexylsulfamic acid; and aminophosphonic acids such as1-aminomethylphosphonic acid, 1-dimethylaminoethylphosphonic acid,2-aminoethyl-phosphonic acid, 2-aminopropylphosphonic acid,4-aminophenylphosphonic acid, 1-aminoethane-1,1-diphosphonic acid,1-amino-1-phenylmethane-1,1-diphosphonic acid,1-dimethylaminoethane-1,1-diphosphonic acid,1-dimethylamino-butane-1,1-diphosphonic acid andethylenediamine-tetramethylenephosphonic acid.

[0247] Furthermore, salts of hydrochloric acid, sulfuric acid, nitricacid, sulfonic acid (e.g., methanesulfonic acid) or oxalic acid withalkali metal, ammonia, lower alkanolamine (e.g., triethanolamine) orlower alkylamine (e.g., triethylamine) may also be suitably used.

[0248] In addition, water-soluble polymers such as polyacrylamide,polyvinyl alcohol, polyvinylpyrrolidone, polyethyleneimine and mineralacid salts thereof, poly-(meth)acrylic acid and metal salts thereof,polystyrene-sulfonic acid and metal salts thereof, alkyl (meth)acrylate,2-acrylamide-2-methyl-1-propanesulfonic acid and metal salts thereof,trialkylammoniummethylstyrene chloride polymers and copolymers thereofwith (meth) acrylic acid, and polyvinylphosphonic acid, may also besuitably used.

[0249] Also, soluble starch, carboxymethyl cellulose, dextrin,hydroxyethyl cellulose, gum arabic, guar gum, sodium alginate, gelatin,glucose and sorbitol may be suitably used. These compounds may be usedeither individually or in combination of two or more thereof.

[0250] In the case of a treatment, this compound is preferably dissolvedin water and/or methyl alcohol to have a concentration of 0.001 to 10 wt%, more preferably from 0.01 to 1.0 wt %. The treatment is performed bydipping the support in the treating solution under the conditions suchthat the temperature is from 25 to 95° C., preferably from 50 to 95° C.,the pH is from 1 to 13, preferably from 2 to 10, for from 10 seconds to20 minutes, preferably from 10 seconds to 3 minutes.

[0251] In the case of using the compound as an undercoat layer for thecoating of the heat-sensitive layer, the compound is similarly dissolvedin water and/or methyl alcohol to have a concentration of 0.001 to 10 wt%, preferably from 0.01 to 1.0 wt %, and if desired, after adjusting thepH with a basic substance such as ammonia, triethylamine and potassiumhydroxide, or an acidic substance such as hydrochloric acid andphosphoric acid, the solution may be used at a pH of 1 to 12. In orderto improve the tone reproducibility of the lithographic printing plateprecursor, a yellow dye may also be added. After the drying, thecoverage of the organic undercoat layer is suitably from 2 to 200 mg/m²,preferably from 5 to 100 mg/m². If the coverage is less than 2 mg/m², asufficiently high effect is not obtained on the prevention of staining,which is the original purpose, whereas if it exceeds 200 mg/m², theimpression capability decreases.

[0252] In order to increase the adhesion between the support and theheat-sensitive layer, an interlayer may be provided. In order toincrease the adhesion, the interlayer generally comprises diazo resin ora phosphoric acid compound capable of adsorbing, for example, toaluminum. The thickness of the interlayer may be freely selected butmust be sufficiently large to attain a uniform bond-forming reactionwith the heat-sensitive layer as the upper layer when exposed. Usually,the coating ratio is, in terms of dry solid, from about 1 to 100 mg/m²,more preferably from 5 to 40 mg/m². The ratio of diazo resin used in theinterlayer is from 30 to 100%, preferably from 60 to 100%.

[0253] Before the above-described treatment or formation of an undercoatlayer, the anodized and then water washed support may be subjected tothe following treatments so as to prevent the anodized film fromdissolving in the developer or fountain solution, to prevent theheat-sensitive layer components from remaining in the film, to improvethe strength of the anodized film, to improve the hydrophilicity of theanodized film or to improve the adhesion to the heat-sensitive layer.

[0254] One of these treatments is a silicate treatment of treating thesupport by contacting the anodized film with an aqueous alkali metalsilicate solution. In this case, the anodized film is contacted with anaqueous solution having an alkali metal silicate concentration of 0.1 to30 wt %, preferably from 0.5 to 15 wt %, and having a pH at 25° C. of 10to 13.5, at a temperature of 5 to 80° C., preferably from 10 to 70° C.,more preferably from 15 to 50°C., for 0.5 to 120 seconds. The contactingmay be made by any method such as dipping or spraying. If the pH is lessthan 10, the aqueous alkali metal silicate solution is gelled, whereasif the pH exceeds 13.5, the anodized film dissolves.

[0255] Examples of the alkali metal silicate for use in the presentinvention include sodium silicate, potassium silicate and lithiumsilicate. Examples of the hydroxide for use in adjusting the pH of theaqueous alkali metal silicate solution include sodium hydroxide,potassium hydroxide and lithium hydroxide. In the above-describedtreating solution, an alkaline earth metal salt or a Group IVb metalsalt may be blended. Examples of the alkaline earth metal salt includenitrates such as calcium nitrate, strontium nitrate, magnesium nitrateand barium nitrate, and water-soluble salts such as sulfate,hydrochloride, phosphate, acetate, oxalate and borate. Examples of theGroup IVb metal salt include titanium tetrachloride, titaniumtrichloride, potassium titanium fluoride, potassium titanium oxalate,titanium sulfate, titanium tetraiodide and zirconium chloride oxide. Thealkaline earth metals and Group IVb metal salts may be used individuallyor in combination of two or more thereof. The metal salt is preferablyused in an amount of 0.01 to 10 wt %, more preferably from 0.05 to 5.0wt %.

[0256] Other than these, various sealing treatments may be used and ingeneral, water vapor sealing, boiling water (hot water) sealing, metalsalt sealing (e.g., chromate/bichromate sealing, nickel acetatesealing), oil and fat impregnation sealing, synthetic resin sealing,low-temperature sealing (with red prussiate or alkaline earth salt),known as a sealing treatment of anodized film, may be used. In view ofthe performance (adhesion with heat-sensitive layer or hydrophilicity)as the support of a printing plate, high-speed treatment, low cost andlow pollution, water vapor sealing is relatively preferred. Examples ofthe method therefor include a method of continuously or discontinuouslycontacting water vapor with anodized film under applied pressure oratmospheric pressure at a relative humidity of 70% or more and watervapor temperature of 95° C. or more for approximately 2 to 180 seconds.Other examples of the sealing treatment include a method where thesupport is dipped in or sprayed with hot water or an aqueous alkalisolution at a temperature on the order of 80 to 100° C. or in place ofthis treatment or in subsequent thereto, the support is dipped in orsprayed with a nitrite solution. Examples of the nitrite includenitrites and ammonium salts thereof, namely, ammonium salts and nitrite,of metals belonging to Groups Ia, IIa, IIb, IIIB, IVb, IVa, VIa, VIIaand VIII of the periodic table. Preferred examples of the metal saltinclude LiO₂, NaNO₂, KNO₂, Mg(NO₂)₂, Ca(NO₂)₂, Zn(NO₃)₂, Al(NO₂)₃,Zr(NO₂)₄, Sn(NO₂)₃, Cr(NO₂)₃, Co(NO₂)₂, Mn(NO₂)₂ and Ni(NO₂)₂. Amongthese, more preferred are alkali metal nitrites. The nitrites can beused in combination of two or more thereof.

[0257] The treating conditions vary depending on the state of thesupport and the kind of the alkali metal and cannot be indiscriminatelydetermined, however, for example, in the case of using sodium nitrite,the alkali conditions may be selected within the range such that theconcentration is generally from 0.001 to 10 wt %, preferably from 0.01to 2 wt %, the bath temperature is generally from room temperature toabout 100° C., preferably from 60 to 90° C., and the treating time isgenerally from 15 to 300 seconds, preferably from 10 to 180 seconds. ThepH of the aqueous nitrite solution is preferably adjusted to 8.0 to11.0, more preferably 8.5 to 9.5. The pH of the aqueous nitrite solutioncan be suitably adjusted to the above-described range using, forexample, an alkali buffer solution. The alkali buffer solution is notparticularly limited, however, for example, a mixed aqueous solution ofsodium hydrogen-carbonate and sodium hydroxide, a mixed aqueous solutionof sodium carbonate and sodium hydroxide, a mixed aqueous solution ofsodium carbonate and sodium hydrogencarbonate, a mixed aqueous solutionof sodium chloride and sodium hydroxide, a mixed aqueous solution ofhydrochloric acid and sodium carbonate, a mixed aqueous solution ofsodium tetraborate and sodium hydroxide and the like may be suitablyused. For the alkali buffer solution, an alkali metal salt other thansodium salt, for example, potassium salt may also be used.

[0258] After the above-described silicate treatment or sealing treatmentis applied, the support may be subjected to a treatment with an acidicaqueous solution or an application of a hydrophilic undercoat disclosedin JP-A-5-278362, or to a treatment of providing an organic layerdisclosed in JP-A-4-282637 and JP-A-7-314937, so as to increase theadhesion to the heat-sensitive layer.

[0259] After the support surface is subjected to these treatments orundercoating, a back coat is applied, if desired, to the back surface ofthe support. The back coat is preferably a coating layer comprising ametal oxide obtained by hydrolyzing and polycondensing an organicpolymer compound described in JP-A-5-45885 and an organic or inorganicmetal compound described in JP-A-6-35174. Among these coating layers,those comprising a metal oxide obtained from an alkoxy compound ofsilicon such as Si(OCH₃)₄, Si(OC₂H₅)₄, Si(OC₃H₇)₄ and Si(OC₄H₉)₄, arepreferred because these alkoxy compounds of silicon are inexpensive andeasily available and the coating layer can have excellent resistanceagainst developer.

[0260] With respect to the preferred properties of support for thelithographic printing plate precursor, the center line average roughnessis from 0.10 to 1.2 μm. If this roughness is less than 0.10 μm, theadhesive property with the heat-sensitive layer decreases and the presslife is seriously reduced, whereas if it exceeds 1.2 μm, the resistanceagainst staining at the printing deteriorates. The color density of thesupport is, in terms of reflection density value, from 0.15 to 0.65. Ifthe color is white in excess of 0.15, the halation is excessivelyintensified at the image exposure and causes troubles in the imageformation, whereas if the color is black in excess of 0.65, the imagecan be hardly viewed at the plate inspection operation after thedevelopment and conspicuously low suitability for plate inspectionresults.

[0261] The lithographic printing plate precursor of the presentinvention can have more excellent on-press developability by using analuminum substrate subjected to surface roughening and then anodizationas the support. In this case, an aluminum substrate subjected further toa silicate treatment is more preferred.

[0262] On the aluminum substrate for use in the printing plate precursorof the present invention, a water-insoluble hydrophilic layer or ahydrophilic layer which generates heat upon laser exposure and at thesame time is insoluble in water may be provided. Or, after aheat-insulating layer comprising an organic polymer is provided on thealuminum substrate so as to impart heat-insulating property, theabove-described water-insoluble hydrophilic layer or hydrophilic layerwhich generates heat upon laser exposure and at the same time isinsoluble in water, may be provided

[0263] For example, a hydrophilic layer comprising silica fine particlesand a hydrophilic resin may be provided on the aluminum substrate.Furthermore, by introducing a light-to-heat converting materialdescribed above into this hydrophilic layer, the layer can work as anexothermic hydrophilic layer. By virtue of this construction, not onlythe heat is prevented from easily escaping into the aluminum substratebut also the substrate can be used as a hydrophilic substrate capable ofgenerating heat upon laser exposure. Furthermore, when an interlayercomprising an organic polymer is provided between the hydrophilic layerand the aluminum substrate, the heat can be more successfully preventedfrom escaping into the aluminum support. In view of the on-pressdevelopability, the support is preferably not porous and if ahydrophilic organic polymer material is contained in a proportion ashigh as 40% or more, the support swells with water and disadvantageouslyencounters difficulties in the clearing of ink.

[0264] The hydrophilic layer for use in the present invention isthree-dimensionally crosslinked and incapable of dissolving in thefountain solution at the lithographic printing using water and/or ink.This layer preferably comprises the following colloid, that is, acolloid comprising a sol-gel converting system of an oxide or hydroxideof beryllium, magnesium, aluminum, silicon, titanium, boron, germanium,tin, zirconium, iron, vanadium, antimony or a transition metal.Depending on the case, the colloid may comprise a composite of theseelements. In the colloid, the element forms a network structure throughoxygen atom and at the same time, non-bonded hydroxyl group and alkoxygroup are present and interspersed in the structure. From the initialhydrolysis condensation stage where active alkoxy group and hydroxylgroup occupy a large proportion, with the progress of the reaction, thecolloid increases in the particle size and becomes inactive. The colloidparticles generally have a particle size of 2 to 500 nm and in the caseof silica, spherical particles having a particle size of 5 to 100 nm arepreferred in the present invention. Like aluminum colloid, feather-likeparticles of 100×10 nm are also effective.

[0265] Furthermore, a pearl neck-like colloid where spherical particleshaving a particle size of 10 to 50 nm are connected to a length of 50 to400 nm may also be used.

[0266] The colloid may be used by itself or may be used in mixture witha hydrophilic resin. In order to accelerate the crosslinking, acrosslinking agent for colloid may be added.

[0267] Usually, the colloid is stabilized by a stabilizer in many cases.In the case of a cationically charged colloid, a compound having ananionic group is added as the stabilizer, and in the case of ananionically charged colloid, a compound having a cationic group is used.For example, silicon colloid is anionically charged, therefore, anamine-based compound is added as the stabilizer, and the aluminumcolloid is cationically charged, therefore, a strong acid such ashydrochloric acid or acetic aid is added. When this colloid is coated ona substrate, a transparent film is formed at an ordinary temperature inmany cases, however, only with the evaporation of the solvent ofcolloid, gelling insufficiently completes. By heating the colloid to atemperature where the stabilizer can be removed, firm three-dimensionalcrosslinking takes place and a hydrophilic layer preferred in thepresent invention can be formed.

[0268] Without using the above-described stabilizer, a hydrolysiscondensation reaction may be performed directly from the startingmaterial (e.g., di- tri- and/or tetra-alkoxysilane) to provide anappropriate sol state, and the sol may be coated as it is on a substrateand dried to complete the reaction. In this case, the three-dimensionalcrosslinking can be accomplished at a lower temperature than in the caseof adding a stabilizer.

[0269] In addition, a colloid obtained by dispersing and stabilizing anappropriate hydrolysis condensation reactant in an organic solvent isalso suitably used in the present invention. In this case, only withevaporation of the solvent, a three-dimensionally crosslinked film canbe obtained. When the solvent is selected from low boiling pointsolvents such as methanol, ethanol, propanol, butanol, ethylene glycolmonomethyl ether, ethylene glycol monoethyl ether and methyl ethylketone, the drying can be achieved at an ordinary temperature. Inparticular, colloids using a methanol or ethanol solvent are useful inthe present invention because curing at a low temperature isfacilitated.

[0270] The hydrophilic resin which is used together with the colloid ispreferably a resin having a hydrophilic group such as hydroxyl,carboxyl, hydroxyethyl, hydroxypropyl, amino, aminoethyl, aminopropyland carboxymethyl. Specific examples of the hydrophilic resin includegum arabic, casein, gelatin, starch derivatives, carboxymethyl celluloseand Na salt thereof, cellulose acetate, sodium alginate, vinylacetate-maleic acid copolymers, styrene-maleic acid copolymers,polyacrylic acids and salts thereof, polymethacrylic acids and saltsthereof, homopolymers and copolymers of hydroxyethyl methacrylate,homopolymers and copolymers of hydroxyethyl acrylate, homopolymers andcopolymers of hydroxypropyl methacrylate, homopolymers and copolymers ofhydroxypropyl acrylate, homopolymers and copolymers of hydroxybutylmethacrylate, homopolymers and copolymers of hydroxybutyl acrylate,polyethylene glycols, hydroxypropylene polymers, polyvinyl alcohols,hydrolyzed polyvinyl acetate having a hydrolysis degree of at least 60wt %, preferably at least 80 wt %, polyvinyl formal, polyvinyl butyral,polyvinyl pyrrolidone, homopolymers and copolymers of acrylamide,homopolymers and copolymers of methacrylamide, homopolymers andcopolymers of N-methylolacrylamide, and homopolymers and copolymers of2-acrylamide-2-methylpropanesulfonic acid and salts thereof.

[0271] The hydrophilic resin is more preferably a water-insolublehydroxyl group-containing polymer and specific examples thereof includehomopolymers and copolymers of hydroxyethyl methacrylate, and copolymersof hydroxyethyl acrylate.

[0272] The hydrophilic resin is used together with the colloid and theadded ratio is, in the case where the hydrophilic resin is soluble inwater, preferably 40 wt % or less based on all solids content in thehydrophilic layer and in the case where the hydrophilic resin is notsoluble in water, preferably 20 wt % or less based on all solidscontent.

[0273] The hydrophilic resin may be used as it is but for the purpose ofincreasing the impression capability at the printing, a crosslinkingagent for hydrophilic resin except for colloid may be added. Examples ofthe crosslinking agent for the hydrophilic resin include initialhydrolysis condensates of formaldehyde, glyoxal, polyisocyanate andtetraalkoxysilane, dimethylol urea and hexamethylolmelamine.

[0274] The hydrophilic layer of the present invention may contain acrosslinking agent of accelerating the crosslinking of the colloid inaddition to the oxide or hydroxide colloid and the hydrophilic resin.This crosslinking agent is preferably initial hydrolysis condensate oftetraalkoxysilane, trialkoxysilylpropyl-N,N,N-trialkylammonium halide,or aminopropyltrialkoxy-silane. The added ratio thereof is preferably 5wt % or less based on all solids content in the hydrophilic layer.

[0275] The hydrophilic layer of the present invention may furthercontain a hydrophilic light-to-heat converting material so as toincrease heat sensitivity. The light-to-heat converting material ispreferably a water-soluble infrared absorbing dye, and the cyanine dyehaving a sulfonic acid group or an alkali metal salt or amine salt groupof sulfonic acid represented by formula (I) can be used to this purpose.The ratio of this dye added is from 1 to 20 wt %, preferably from 5 to15 wt %, based on the entire amount of the hydrophilic layer.

[0276] In the present invention, the three-dimensionally crosslinkedhydrophilic layer coated preferably has a thickness of 0.1 to 10 μm,preferably from 0.5 to 5 μm. If the thickness is excessively small, thehydrophilic layer has poor durability and the impression capability atthe printing decreases, whereas if it is too large, the resolutiondecreases.

[0277] The interlayer comprising an organic polymer is described below.The organic polymer which can be used in the interlayer may be anyorganic polymer commonly used, such as polyurethane resin, polyesterresin, acrylic resin, cresol resin, resol resin, polyvinyl acetal resinand vinyl resin. The amount coated thereof is preferably from 0.1 to 5.0g/m². If the amount coated is less than 0.1 g/m², the heat-insulatingeffect is low, whereas if it exceeds 5.0 g/m², the press life in thenon-image area deteriorates.

[0278] The lithographic printing plate precursor of the presentinvention can form an image by the exposure with a high output laser,however, a writing machine such as thermal head may also be used. In thepresent invention, a laser of emitting light in the infrared or nearinfrared region is preferred, and a laser diode of emitting light in thenear infrared region is more preferred.

[0279] In this case, when a microcapsule is used in the heat-sensitivelayer and the outer wall of the microcapsule is capable of rupturing bythe heat used for the image formation, the exposure must be performedwith an energy amount sufficiently large to rupture the outer wall.

[0280] In the case of not rupturing the outer wall of the capsule by theheat used for the image formation, the exposure must be performed withan energy not to cause rupturing of the outer wall.

[0281] As such, the lithographic printing plate precursor of the presentinvention can be manufactured. This lithographic printing plateprecursor can perform the recording with an infrared laser.

[0282] The recording may be thermally made using an ultraviolet lamp ora thermal head, however, in the present invention, the image exposure ispreferably performed using a solid laser or semiconductor laser capableof radiating an infrared light at the wavelength of 760 to 1,200 nm. Thelaser output is preferably 100 mW or more and in order to shorten theexposure time, a multi-beam laser device is preferably used. Theexposure time is preferably 20μseconds or less per one picture element.The energy irradiated on the recording material is preferably from 10 to300 mJ/cm².

[0283] The thus exposed plate is fixed to a cylinder of the printingmachine without passing through any processing. Using this fixed plate,the printing can be performed by the following procedures.

[0284] (1) A method of supplying fountain solution to the printing plateand after the development on the press, further supplying ink to startthe printing.

[0285] (2) A method of supplying fountain solution and ink to theprinting plate and after the development on the press, starting theprinting.

[0286] (3) A method of supplying ink to the plate and simultaneouslywith the supply of fountain solution, feeding paper to start printing.

[0287] Also, as described in Japanese Patent No. 2938398, the plate maybe fixed to the cylinder of the printing machine, exposed by a lasermounted on the printing machine, and developed on the press by applyingfountain solution and/or ink thereto. The plate is preferablydevelopable with water or an aqueous solution or capable of fixing tothe printing machine as it is without passing through development andbeing used for the printing.

EXAMPLES

[0288] The present invention is described in greater detail below byreferring to the Examples, however, the present invention should not beconstrued as being limited thereto.

Example I-1 to I-7 and Comparative Examples I-1 to I-3

[0289] Preparation of Support (1) (Preparation of Aluminum Support)

[0290] A molten metal of JIS A01505 alloy containing 99.5% or morealuminum, 0.30% of Fe, 0.10% of Si, 0.02% of Ti and 0.013% of Cu wassubjected to a cleaning treatment and then cast. In the cleaningtreatment, the molten metal was subjected to a degassing treatment andthen to a ceramic tube filter treatment, for removing unnecessary gassuch as a hydrogen gas. The casting was performed by the DC castingmethod. The solidified ingot having a plate thickness of 500 nm wasscalped to 10 mm from the surface, subjected to a homogenizationtreatment at 550° C. for 10 hours so as to prevent the intermetalliccompound from becoming coarse. Subsequently, the plate was hot-rolled at400° C., intermediate-annealed at 500° C. for 60 seconds in a continuousannealing furnace and then cold-rolled to obtain an aluminum rolledplate having a thickness of 0.30 mm. By controlling the roughness of theroller, the center line average surface roughness (Ra) after the coldrolling was controlled to 0.2 μm. Thereafter, the plate was applied witha tension leveler to improve the planeness.

[0291] Subsequently, the plate was surface-treated to obtain a supportfor a lithographic printing plate.

[0292] The plate was degreased with an aqueous 10% sodium aluminate at50° C. for 30 seconds to remove the rolling oil on the aluminum platesurface and then treated for neutralization and desmutting with anaqueous 30% sulfuric solution at 50° C. for 30 seconds.

[0293] Then, the aluminum plate was subjected to a so-called grainingtreatment of roughening the support surface so as to attain goodadhesion between the support and the heat-sensitive layer and at thesame time to impart water receptivity to the non-image area. Whilekeeping an aqueous solution containing 1% of nitric acid and 0.5% ofaluminum nitrate at 45° C. and passing the aluminum web through theaqueous solution, the electrolytic graining was performed by applying analternation-wave electric current at a current density of 20 A/dm² and aduty ratio of 1.1 to a quantity of electricity of 240 C/dm² in the anodeside from an indirect power supply cell. Thereafter, the plate wasetched with an aqueous 10% sodium aluminate solution at 5° C. for 30seconds and then treated with an aqueous 30% sulfuric acid solution forneutralization and desmutting at 50° C. for 30 seconds (AluminumSubstrate A).

[0294] In order to improve the abrasion resistance, chemical resistanceand water receptivity, an oxide film was formed on the support byanodization. An aqueous 20% sulfuric acid solution at 35° C. was used asthe electrolyte and while transporting the aluminum web through theelectrolyte, the electrolytic treatment was performed with a d.c.current at 14 A/dm² from an indirect power supply cell to form an anodicoxide film of 2.5 g/m² (Aluminum Substrate B)

[0295] Thereafter, in order to ensure the hydrophilicity in thenon-image area of the printing plate, the substrate was treated withsilicate. In the treatment, while keeping an aqueous 1.5% No. 3 sodiumsilicate solution (i.e., sodium tetrasilicate solution) at 70° C., thealuminum web was transported therethrough such that the contact time was15 seconds, and then washed with water. The amount of Si attached was 10mg/m². The thus-prepared support had Ra (center line average surfaceroughness) of 0.25 μm (Aluminum Substrate C).

[0296] Preparation of Support (2) (Preparation of Support ComprisingAluminum Substrate Having Provided Thereon Exothermic HydrophilicLayer):

[0297] In 240 g of methanol, 45.2 g of methanol silica sol (produced byNissan Chemical, a colloid comprising a methanol solution containing 30wt % of silica particles of 10 to 20 nm), 1.52 g of poly-2-hydroxyethylmethacrylate and 3.2 g of infrared absorbing dye. (I-32) were dissolved.The resulting solution was coated on Aluminum Substrate C by bar coatingand dried in an oven at 100° C. for 30 seconds. The amount coated was1.0 g/m².

[0298] Preparation of Support (3) (Preparation of Support ComprisingAluminum Substrate Having Provided Thereon Heat-Insulating Layer andFurther Provided Thereon Exothermic Hydrophilic Layer):

[0299] Coating of Heat-Insulating Layer:

[0300] In 100 g of methyl ethyl ketone and 90 g of methyl lactate, 10 gof polyvinyl butyral resin was dissolved. The resulting solution wascoated on Aluminum Substrate C by bar coating and dried in an oven at100° C. for 1 minute. The amount coated was 0.5 g/m².

[0301] Coating of Exothermic Hydrophilic Layer:

[0302] In 240 g of methanol, 45.2 g of methanol silica sol, 1.52 g ofpoly-2-hydroxyethyl methacrylate and 3.2 g of infrared absorbing dye(I-32) were dissolved. The resulting solution was coated on thepreviously provided heat-insulating layer by bar coating and dried in anoven at 100° C. for 30 seconds. The amount coated was 1.0 g/m².

[0303] Synthesis of Fine Particulate Polymer Capable of Combining byHeat:

[0304] Synthesis (1) of Fine Particulate Polymer Capable of Combining byHeat:

[0305] To a reaction system, 2.0 g of glycidyl methacrylate, 13.0 g ofmethyl methacrylate and 200 ml of an aqueous polyoxyethylene phenolsolution (concentration: 9.8×10⁻³ mol/liter) were added, and whilestirring at 250 rpm, the inside of the system was purged with nitrogengas. The resulting solution was adjusted to 25° C. and thereto 10 ml ofan aqueous cerium(IV) ammonium salt solution (concentration: 0.984×10⁻³mol/liter) was added. At this time, an aqueous ammonium nitrate solution(concentration: 58.8×10⁻³ mol/liter) was added to adjust the pH to 1.3to 1.4. Thereafter, the solution was stirred for 8 hours. Thethus-obtained solution had a solids concentration of 9.5% and an averageparticle size of 0.4 μm.

[0306] Synthesis (2) of Fine Particulate Polymer Capable of Combining byHeat:

[0307] 7.5 g of allyl methacrylate and 7.5 g of styrene were polymerizedin the same manner. The thus-obtained solution had a solidsconcentration of 9.5% and an average particle size of 0.4 μm.

[0308] Synthesis (3) of Fine Particulate Polymer Capable of Combining byHeat:

[0309] In a solution containing 12.0 g of ethyl acetate and 6.0 ofmethyl ethyl ketone, 6.5 of Epicoat 1007 (Yuka Shell Epoxy K.K.), 1.0 gof light-to-heat converting material (I-34) and 0.1 g of an anionsurfactant (“Pionine A41C” produced by Takemoto Yushi K.K.) weredissolved. The resulting solution was added to 36 g of 4% aqueoussolution of PVA 205 (Kuraray Co., Lt.) and then emulsion-dispersed byhomogenizer at 15,000 rpm for 15 minutes.

[0310] Therefore, further the dispersed solution was heated at 60° C.and stirred for 90 minutes, and then a solvent in the solution wasevaluated to obtain a fine particle polymer having an average particlesize of 0.20 μm and a solids concentration of 18.0%.

[0311] Synthesis (4) of Fine Particulate Polymer (Comparative Example)(Not Having a Reactive Group):

[0312] 15 g of styrene was polymerized in the same manner. Thethus-obtained solution had a solids concentration of 9.0% and an averageparticle size of 0.3 μm.

[0313] Coating of Heat-Sensitive Layer:

[0314] Coating solutions each having the following compositioncontaining the heat-fusible fine particulate polymer of SynthesisExample (1), (2) (3) or (4) were prepared and coated on Support (1), (2)or (3) prepared above to form a heat-sensitive layer.

[0315] Composition of Coating Solution for Heat-Sensitive Layer: Water 100 g Fine Particulate Polymer (1), (2), (3) or   5 g (4) synthesizedabove (in terms of solids content) Polyhydroxyethyl acrylate (weightaverage  0.5 g molecular weight: 25,000) Infrared Absorbing Dye (I-32) 0.3 g

[0316] The coating solution was bar-coated and then dried in an oven at80° C. for 120 seconds. The coated amount was 0.5 g/m².

[0317] The thus-obtained lithographic printing plate capable of on-pressdevelopment was exposed in Trendsetter 3244VFS manufactured by Creo, onwhich a water cooling 40W infrared semiconductor laser was mounted,under the conditions such that the output was 9 W, the rotation numberof the outer drum was 210 rpm, the plate surface energy was 100 mJ/cm²and the resolution was 2,400 dpi. Thereafter, without passing throughdevelopment, the plate was fixed to a cylinder of a printing machineHeider SOR-M and by supplying fountain solution, then supplying ink andfurther feeding paper, printing was performed. All plates could beon-press developed without any problem and used for printing. The numberof sheets of the printed matter obtained with each plate is shown inTable I-1 below. TABLE I-1 Heat-Sensitive Number of Support LayerPrintable Sheets Example I-1 (1) Fine Particulate 5,000 Polymer (1)Example I-2 (2) Fine Particulate 10,000 Polymer (1) Example I-3 (3) FineParticulate 15,000 Polymer (1) Example I-4 (1) Fine Particulate 3,000Polymer (2) Example I-5 (2) Fine Particulate 6,000 Polymer (2) ExampleI-6 (3) Fine Particulate 10,000 Polymer (2) Example I-7 (1) FineParticulate 20,000 Polymer (3) Comparative (1) Fine Particulate 1,000Example I-1 Polymer (4) Comparative (2) Fine Particulate 1,500 ExampleI-2 Polymer (4) Comparative (3) Fine Particulate 2,000 Example I-3Polymer (4)

[0318] As seen from the results above, the press life is better with thefine particulate polymer having a reactive group. Also, the press lifeis better with the support comprising an aluminum substrate havingprovided thereon an exothermic hydrophilic layer or the supportcomprising an aluminum substrate having provided thereon aheat-insulating layer and further provided thereon an exothermichydrophilic layer.

Example I-8

[0319] A coating solution for the heat-sensitive layer comprising thefollowing composition was coated on Support (3). Water  100 g FineParticulate Polymer (2) synthesized   5 g above (in terms of solidscontent) Polyacrylic acid (weight average  0.5 g molecular weight:25,000) Sorbitol triacrylate  1.0 g Infrared Absorbing Dye (I-31)  0.3 g

[0320] The thus-obtained plate was exposed and used for printing in thesame manner as in Example I-1 to I-7, as a result, 20,000 sheets couldbe printed without any abnormality.

Example I-9

[0321] A coating solution for the heat-sensitive layer comprising thefollowing composition was coated on Support (3). Water  100 g FineParticulate Polymer (1) synthesized   5 g above (in terms of solidscontent) Polyacrylic acid (weight average  0.5 g molecular weight:25,000) Diethylenetriamine  1.0 g Infrared Absorbing Dye (I-31)  0.3 g

[0322] The thus-obtained plate was exposed in Luxel T-9000CTPmanufactured by Fuji Photo Film Co., Ltd., on which a multi-channellaser head was mounted, under the conditions that the output was 250 mWper 1 beam, the rotation number of the outer drum was 800 rpm and theresolution was 2,400 dpi. Using this plate, printing was performed inthe same manner as in Example I-1 to I-7, as a result, 30,000 sheetscould be printed without any abnormality.

Examples I-10 to I-12

[0323] Lithographic printing plate precursors were prepared, imageexposed and used for printing in the same manner as in Example I-1except for using Aluminum Substrates A to C obtained in the Preparationof Support (1), and then evaluated on the on-press developability.

[0324] The on-press developability was evaluated by examining how large% the shadow part of a halftone image of 150 lines/inch on the 100thprinted matter from the initiation of printing could be reproduced andas the value obtained was higher, the on-press developability wasevaluated more excellent.

[0325] The results obtained are shown in Table I-2 below. TABLE I-2Resistance against Staining at Printing Reproducibility of AluminumSubstrate Shadow Part (%) Example I-10 Aluminum Substrate A 90 ExampleI-11 Aluminum Substrate B 95 Example I-12 Aluminum Substrate C 98

[0326] It is seen from Table I-2 that when an aluminum substratesubjected to anodization or further to silicate solution was used as thesupport, the on-press develop-ability was excellent.

[0327] In the lithographic printing plate precursor of the presentinvention, the heat-sensitive layer provided on a hydrophilic supportcontains a fine particulate polymer capable of combining by heat at thetime of image formation and having a functional group capable ofreacting with a functional group present in another fine particulatepolymer or with a functional group present in another component in theheat-sensitive layer, whereby the lithographic printing plate precursorcan have high sensitivity and high press life, provide a printed matterfree of residual color and staining, exhibit good on-pressdevelopability and print a larger number of printed matters. By furtherincorporating a light-to-heat converting material into theheat-sensitive layer or providing a layer containing a light-to-heatconverting material between the support and the heat-sensitive layer,plate-making can be performed using scan exposure based on digitalsignals. Furthermore, by using an aluminum substrate subjected toanodization or further to silicate treatment as the support, moreexcellent on-press developability can be obtained.

Examples II-1 to II-6 and Comparative Examples II-1 to II-3

[0328] Preparation of Support (1) (Preparation of Aluminum Substrate)

[0329] As the Support (1), Aluminum Substrates A, B and C were preparedin the same manner as in Examples I-1 to I-7. Preparation of Support (2)(preparation of support comprising aluminum substrate having providedthereon exothermic hydrophilic layer)

[0330] Support (2) was prepared in the same manner as in Examples I-1 toI-7.

[0331] Preparation of Support (3) (Preparation of Support ComprisingAluminum Substrate Having Provided Thereon Heat-Insulating HydrophilicLayer)

[0332] Support (3) was prepared in the same manner as in Examples I-1 toI-7.

[0333] Synthesis of Fine Particulate Polymer Incapable of Combining byHeat:

[0334] Synthesis (1) of Fine Particulate Polymer Incapable of Combiningby Heat:

[0335] To a reaction system, 7.5 g of glycidyl methacrylate, 3.5 g oftrimethylolpropane triacrylate, 4.0 g of methyl methacrylate and 200 mlof an aqueous polyoxyethylene phenol solution (concentration: 9.8×10⁻³mol/liter) were added, and while stirring at 250 rpm, the inside of thesystem was purged with nitrogen gas. The resulting solution was adjustedto 25° C. and thereto 10 ml of an aqueous cerium(IV) ammonium saltsolution (concentration: 0.984×10⁻³ mol·l⁻¹) was added. At this time, anaqueous ammonium nitrate solution (concentration: 58.8×10⁻³ mol·l⁻¹) wasadded to adjust the pH to 1.3 to 1.4. Thereafter, the solution wasstirred for 8 hours. The thus-obtained solution had a solidsconcentration of 9.5% and an average particle size of 0.4 μm.

[0336] Synthesis (2) of Fine Particulate Polymer Incapable of Combiningby Heat:

[0337] 7.5 g of allyl methacrylate, 5.5 g of styrene and 2.0 g ofdivinyl benzene were polymerized in the same manner. The thus-obtainedsolution had a solids concentration of 9.5% and an average particle sizeof 0.4 μm.

[0338] Synthesis (3) of Fine Particulate Polymer (Comparative Example)(Not Having a Reactive Group):

[0339] 15 g of styrene was polymerized in the same manner. Thethus-obtained solution had a solids concentration of 9.0% and an averageparticle size of 0.3 μm.

[0340] Coating of Heat-Sensitive Layer:

[0341] Coating solutions each having the following compositioncontaining the fine particulate polymer of Synthesis Example (1), (2) or(3) were prepared and coated on Support (1), (2) or (3) prepared aboveto form a heat-sensitive layer.

[0342] Composition of Coating Solution for Heat-Sensitive Layer: Water 100 g Fine Particulate Polymer (1), (2) or (3)   5 g synthesized above(in terms of solids content) Polyhydroxyethyl acrylate (weight average 0.5 g molecular weight: 25,000) Infrared Absorbing Dye (I-32)  0.3 g

[0343] The coating solution was bar-coated and then dried in an oven at100° C. for 60 seconds. The coated amount was 0.5 g/m².

[0344] The thus-obtained lithographic printing plate capable of on-pressdevelopment was exposed in Trendsetter 3244VFS manufactured by Creo, onwhich a water cooling 40W infrared semiconductor laser was mounted,under the conditions such that the output was 9 W, the rotation numberof the outer drum was 210 rpm, the plate surface energy was 100 mJ/cm²and the resolution was 2,400 dpi. Thereafter, without passing throughdevelopment, the plate was fixed to a cylinder of a printing machineHeider SOR-M and by supplying fountain solution, then supplying ink andfurther feeding paper, printing was performed. All plates could beon-press developed without any problem and used for printing.Furthermore, the plate was aged at 60° C. for 3 days and then on-pressdeveloped to examine the level of staining. The number of sheets of theprinted matter obtained with each plate is shown in Table II-1 below.TABLE II-1 Heat-Sensitive Number of Sheets Staining Support LayerPrinted After Aging Example II-1 (1) Fine Particulate 5,000 not stainedPolymer (1) Example II-2 (2) Fine Particulate 10,000 not Polymer (1)stained Example II-3 (3) Fine Particulate 15,000 not Polymer (1) stainedExample II-4 (1) Fine Particulate 3,000 not Polymer (2) stained ExampleII-5 (2) Fine Particulate 6,000 not Polymer (2) stained Example II-6 (3)Fine Particulate 10,000 not Polymer (2) stained Comparative (1) FineParticulate 1,000 stained Example II-1 Polymer (3) Comparative (2) FineParticulate 1,500 stained Example II-2 Polymer (3) Comparative (3) FineParticulate 2,000 stained Example II-3 Polymer (3)

[0345] It is seen from these results that when a fine particulatepolymer incapable of combining by heat used for the image formation wasused, good press life was obtained. Furthermore, in the case where thesupport was an aluminum substrate having provided thereon an exothermichydrophilic layer or an aluminum substrate having provided thereon aheat-insulating layer and further provided thereon an exothermichydrophilic layer, the press life was more excellent.

Example II-7

[0346] A coating solution for the heat-sensitive layer comprising thefollowing composition was coated on Support (3). Water  100 g FineParticulate Polymer (2) synthesized   5 g above (in terms of solidscontent) Polyacrylic acid (weight average  0.5 g molecular weight:25,000) Sorbitol triacrylate  1.0 g Infrared Absorbing Dye (I-31)  0.3 g

[0347] The thus-obtained plate was exposed and used for printing in thesame manner as in Example II-1 to II-6, as a result, 20,000 sheets couldbe printed without any abnormality.

Example II-8

[0348] A coating solution for the heat-sensitive layer comprising thefollowing composition was coated on Support (3). Water  100 g FineParticulate Polymer (1) synthesized   5 g above (in terms of solidscontent) Polyacrylic acid (weight average  0.5 g molecular weight:25,000) Diethylenetriamine  1.0 g Infrared Absorbing Dye (I-31)  0.3 g

[0349] The thus-obtained plate was exposed in Luxel T-9000CTPmanufactured by Fuji Photo Film Co., Ltd., on which a multi-channellaser head was mounted, under the conditions that the output was 250 mWper 1 beam, the rotation number of the outer drum was 800 rpm and theresolution was 2,400 dpi. Using this plate, printing was performed inthe same manner as in Example II-1 to II-6, as a result, 30,000 sheetscould be printed without any abnormality.

Examples II-9 to II-11

[0350] Lithographic printing plate precursors were prepared, imageexposed and used for printing in the same manner as in Example II-1except for using Aluminum Substrates A to C obtained in the Preparationof Support (1), and then evaluated on the on-press developability.

[0351] The on-press developability was evaluated by examining how large% the shadow part of a halftone image of 150 lines/inch on the 100thprinted matter from the initiation of printing could be reproduced andas the value obtained was higher, the on-press developability wasevaluated more excellent.

[0352] The results obtained are shown in Table II-2 below. TABLE II-2Resistance against Staining at Printing Reproducibility of AluminumSubstrate Shadow Part (%) Example II-9 Aluminum Substrate A 90 ExampleII-10 Aluminum Substrate B 95 Example II-11 Aluminum Substrate C 98

[0353] It is seen from Table I-2 that when an aluminum substratesubjected to anodization or further to silicate solution was used as thesupport, the on-press develop-ability was excellent.

[0354] In the lithographic printing plate precursor of the presentinvention, the heat-sensitive layer provided on a hydrophilic supportcontains a fine particulate polymer incapable of combining by heat usedfor the image formation and having a functional group capable ofreacting with a functional group present in another fine particulatepolymer or with a functional group present in another component in theheat-sensitive layer, whereby the lithographic printing plate precursorcan have high sensitivity and high press life, provide a printed matterfree of residual color and staining, exhibit good on-pressdevelopability even after aging, and print a larger number of printedmatters. By further incorporating a light-to-heat converting materialinto the heat-sensitive layer or providing a layer containing alight-to-heat converting material between the support and theheat-sensitive layer, plate-making can be performed using scan exposurebased on digital signals. Furthermore, by using an aluminum substratesubjected to anodization or further to silicate treatment as thesupport, more excellent on-press developability can be obtained.

Examples III-1 to II-6 and Comparative Examples III-1 to III-3

[0355] Preparation of Support (1) (Preparation of Aluminum Substrate)

[0356] As the Support (1), Aluminum Substrates A, B and C were preparedin the same manner as in Examples I-1 to I-7.

[0357] Preparation of Support (2) (Preparation of Support ComprisingAluminum Substrate Having Provided Thereon Exothermic Hydrophilic Layer)

[0358] Support (2) was prepared in the same manner as in Examples I-1 toI-7.

[0359] Preparation of Support (3) (Preparation of Support ComprisingAluminum Substrate Having Provided Thereon Heat-Insulating HydrophilicLayer)

[0360] Support (3) was prepared in the same manner as in Examples I-1 toI-7.

[0361] Synthesis of Microcapsule:

[0362] Synthesis (1) of Microcapsule Having Outer Wall Incapable ofRupturing by Heat:

[0363] As the oil phase component, 30 g of D-110 N (produced by TakedaYakuhin Kogyo), 10 g of Karenz MOI (produced by Showa Denko)(2-methacryloyloxyethyl isocyanate), 10 g of trimethylolpropanetriacrylate and 10 g of Pionine A41C (produced by Takemoto. Yushi)(allyl methacrylate and butyl methacrylate copolymer (60/40 by mol))were dissolved in 80 g of ethyl acetate. As the aqueous phase component,120 g of a 4% aqueous solution of PVA205 (produced by Kuraray) wasprepared. The oil phase component and the aqueous phase component wereemulsified using a homogenizer at 10,000 rpm. Thereafter, 40 g of waterwas added and the resulting solution was stirred at room temperature for30 minutes and further at 40° C. for 3 hours. The thus-obtainedmicrocapsule solution had a solids concentration of 20% and an averageparticle size of 0.25 μm.

[0364] Synthesis (2) of Microcapsule Having Outer Wall Incapable ofRupturing by Heat:

[0365] As the oil phase component, 40 g of D-110 N (produced by TakedaYakuhin Kogyo), 20 g of diethylene glycol diglycidyl ether and 0.1 g ofPionine A41C (produced by Takemoto Yushi) were dissolved in 80 g ofethyl acetate. As the aqueous phase component, 120 g of a 4% aqueoussolution of PVA205 (produced by Kuraray) was prepared. The oil phasecomponent and the aqueous phase component were emulsified using ahomogenizer at 10,000 rpm. Thereafter, 40 g of water was added and theresulting solution was stirred at room temperature for 30 minutes andfurther at 40° C. for 3 hours. The thus-obtained microcapsule solutionhad a solids concentration of 20% and an average particle size of 0.18μm

[0366] Synthesis (1) of Fine Particulate Polymer (Comparative Example)(Not Having a Reactive Group):

[0367] To a reaction system, 15 g of styrene and 200 ml of an aqueouspolyoxyethylene phenol solution (concentration: 9.84×10⁻³ mol·l⁻¹) wereadded and while stirring at 250 rpm, the inside of the system was purgedwith nitrogen gas. The resulting solution was adjusted to 25° C. andthereto 10 ml of an aqueous cerium(IV) ammonium salt solution(concentration: 0.984×10⁻³ mol·l⁻¹) was added. At this time, an aqueousammonium nitrate solution (concentration: 58.8×10⁻³ mol·l⁻¹) was addedto adjust the pH to 1.3 to 1.4. Thereafter, the solution was stirred for8 hours. The thus-obtained solution had a solids concentration of 9.5%and an average particle size of 0.4 μm.

[0368] Coating of Heat-Sensitive Layer:

[0369] Coating solutions each having the following compositioncontaining the microcapsule of Synthesis Example (1) or (2) or fineparticulate polymer of Synthesis Example (1) were prepared and coated onSupport (1), (2) or (3) prepared above to form a heat-sensitive layer.

[0370] Composition of Coating Solution for Heat-Sensitive Layer: Water70 g 1-Methoxy-2-propanol 30 g Microcapsule (1) or (2) or Fine 5 gParticulate Polymer (1) synthesized above (in terms of solids content)Polyhydxoxyethyl acrylate 0.5 g Sulfate of p-diazophenylamine 0.3 gInfrared Absorbing Dye (I-32) 0.3 g

[0371] The coating solution was bar-coated and then dried in an oven at100° C. for 60 seconds. The coated amount was 0.5 g/m².

[0372] The thus-obtained lithographic printing plate capable of on-pressdevelopment was exposed in Trendsetter 3244VFS manufactured by Creo, onwhich a water cooling 40W infrared semiconductor laser was mounted,under the conditions such that the output was 9 W, the rotation numberof the outer drum was 105 rpm, the plate surface energy was 200 mJ/cm²and the resolution was 2,400 dpi. Thereafter, without passing throughdevelopment, the plate was fixed to a cylinder of a printing machineHeider SOR-M and by supplying fountain solution, then supplying ink andfurther feeding paper, printing was performed. All plates could beon-press developed without any problem and used for printing. The numberof sheets of the printed matter obtained with each plate is shown inTable III-1 below. TABLE III-1 Number of Staining Heat-Sensitive SheetsAfter Support Layer Printed Aging Example III-1 (1) Microcapsule (1)5,000 not stained Example III-2 (2) Microcapsule (1) 10,000 not stainedExample III-3 (3) Microcapsule (1) 15,000 not stained Example III-4 (1)Microcapsule (2) 3,000 not stained Example III-5 (2) Microcapsule (2)7,000 not stained Example III-6 (3) Microcapsule (2) 10,000 not stainedComparative (1) Fine Particulate 1,000 stained Example III-1 Polymer (1)Comparative (2) Fine Particulate 1,500 stained Example III-2 Polymer (1)Comparative (3) Fine Particulate 2,000 stained Example III-3 Polymer (1)

[0373] It is seen from these results that lithographic printing plateshaving a heat-sensitive layer containing the microcapsule had excellentpress life. Furthermore, in the case where the support was an aluminumsubstrate having provided thereon an exothermic hydrophilic layer or analuminum substrate having provided thereon a heat-insulating layer andfurther provided thereon an exothermic hydrophilic layer, the press lifewas more excellent.

[0374] It is also seen that by using Microcapsule (1) or (2) havingouter wall incapable of rupturing by heat upon irradiation of a laser,the staining scarcely occurred when the printing was performed afteraging at 60° C. for 3 days, as compared with the case using FineParticulate Polymer (1).

Example III-7

[0375] A coating solution for the heat-sensitive layer comprising thefollowing composition was coated on Support (3). Water  100 g1-Methoxy-2-propanol   30 g Microcapsule (1) synthesized above (in   5 gterms of solids content) Polyacrylic acid (weight average  0.5 gmolecular weight: 25,000) Sorbitol triacrylate  1.0 g Infrared AbsorbingDye (I-31)  0.3 g Sulfate of t-butyldiphenyl iodonium  0.3 g

[0376] The thus-obtained plate was exposed in Luxel T-9000CTPmanufactured by Fuji Photo Film Co., Ltd., on which a multi-channellaser head was mounted, under the conditions that the output was 250 mWper 1 beam, the rotation number of the outer drum was 400 rpm and theresolution was 2,400 dpi. Using this plate, printing was performed inthe same manner as in Example III-1 to III-6, as a result, 15,000 sheetscould be printed without any abnormality.

Example III-8

[0377] A coating solution for the heat-sensitive layer comprising thefollowing composition was coated on Support (3). Water  100 g1-Methoxy-2-propanol   30 g Microcapsule (2) (in terms of solids   5 gcontent) Polyacrylic acid (weight average  0.5 g molecular weight:25,000) Diethylenetriamine  1.0 g Infrared Absorbing Dye (I-31)  0.3 gSulfate of t-butyldiphenyl iodonium  0.3 g

[0378] The thus-obtained plate was exposed in Luxel T-9000CTPmanufactured by Fuji Photo Film Co., Ltd., on which a multi-channellaser head was mounted, under the conditions that the output was 250 mWper 1 beam, the rotation number of the outer drum was 400 rpm and theresolution was 2,400 dpi. Using this plate, printing was performed inthe same manner as in Example III-1 to III-6, as a result, 30,000 sheetscould be printed without any abnormality.

Examples III-9 to III-11

[0379] Lithographic printing plate precursors were prepared, imageexposed and used for printing in the same manner as in Examples III-1 toIII-6 except for preparing the following Microcapsules (3) and (4) andcoating a coating solution for the heat-sensitive layer having thefollowing composition on Support (1).

[0380] Synthesis (3) of Microcapsule Having Outer Wall Incapable ofRupturing by Heat:

[0381] As the oil phase component, 30 g of D-110 N (produced by TakedaYakuhin Kogyo), 10 g of 2-methacryloyloxyethyl isocyanate, 9 g oftrimethylolpropane diacrylate, 8 g of allyl methacrylate and butylacrylate copolymer (60/40 by mol), 3 g of Infrared Absorbing Dye (I-33)and 0.1 g of Pionine A41C (produced by Takemoto Yushi) were dissolved in80 g of ethyl acetate. As the aqueous phase component, 120 g of a 4%aqueous solution of PVA205 (produced by Kuraray) was prepared. The oilphase component and the aqueous phase component were emulsified using ahomogenizer at 10,000 rpm. Thereafter, 40 g of water was added and theresulting solution was stirred at room temperature for 30 minutes andfurther at 40° C. for 3 hours. The thus-obtained microcapsule solutionhad a solids concentration of 20% and an average particle size of 0.20μm.

[0382] Synthesis (4) of Microcapsule Having Outer Wall Incapable ofRupturing by Heat:

[0383] As the oil phase component, 30 g of D-110 N (produced by TakedaYakuhin Kogyo), 10 g of 2-methacryloyloxyethyl isocyanate, 9 g oftrimethylolpropane diacrylate, 8 g of allyl methacrylate and butylacrylate copolymer (60/40 by mol), 3 g of Infrared Absorbing Dye (I-33),0.1 g of Pionine A41C (produced by Takemoto Yushi) and 1.0 g of2,2′-azobisisobutyronitrile were dissolved in 80 g of ethyl acetate. Asthe aqueous phase component, 120 g of a 4% aqueous solution of PVA205(produced by Kuraray) was prepared. The oil phase component and theaqueous phase component were emulsified using a homogenizer at 10,000rpm. Thereafter, 40 g of water was added and the resulting solution wasstirred at room temperature for 30 minutes and further at 40° C. for 3hours. The thus-obtained microcapsule solution had a solidsconcentration of 20% and an average particle size of 0.25 μm.

[0384] Composition of Coating Solution for Heat-Sensitive Layer ofExample III-9: Water  70 g 1-Methoxy-2-propanol  30 g Microcapsule (3)synthesized above   5 g Polyhydroxyethyl acrylate 0.5 gp-Diazophenylamine sulfate 0.3 g

[0385] Composition of Coating Solution for Heat-Sensitive Layer ofExample III-10: Water  70 g 1-Methoxy-2-propanol  30 g Microcapsule (3)synthesized above   5 g Polyhydroxyethyl acrylate 0.5 gp-Diazophenylamine sulfate 0.3 g Infrared Absorbing Dye (I-32) 0.1 g

[0386] Composition of Coating Solution for Heat-Sensitive Layer ofExample III-11: Water  70 g 1-Methoxy-2-propanol  30 g Microcapsule (4)synthesized above   5 g Polyhydroxyethyl acrylate 0.5 gp-Diazophenylamine sulfate 0.3 g Infrared Absorbing Dye (I-32) 0.1 g

[0387] In Examples III-9 and II-10, the number of sheets which could beprinted was 10,000, and in Example III-11, the number of sheets whichcould be printed was 15,000, revealing high press life as compared withExample III-1 (5,000 sheets) where the microcapsule contained nolight-to-heat converting substance. By further incorporating a compoundcapable of initiating and accelerating the reaction into themicrocapsule, higher press life could be obtained. When printing wasperformed after aging at 60° C. for 3 days, the resistance againststaining was on the same level as in Example III-1.

Examples III-12 to III-14

[0388] Lithographic printing plate precursors were prepared, imageexposed and used for printing in the same manner as in Example III-1except for using Aluminum Substrates A to C obtained in the Preparationof Support (1), and then evaluated on the on-press developability.

[0389] The on-press developability was evaluated by examining how large% the shadow part of a halftone image of 150 lines/inch on the 100thprinted matter from the initiation of printing could be reproduced andas the value obtained was higher, the on-press developability wasevaluated more excellent.

[0390] The results obtained are shown in Table III-2 below. TABLE III-2Resistance against Staining at Printing Reproducibility of AluminumSubstrate Shadow Part (%) Example III-12 Aluminum Substrate A 90 ExampleIII-13 Aluminum Substrate B 95 Example III-14 Aluminum Substrate C 98

[0391] It is seen from Table III-2 that when an aluminum substratesubjected to anodization or further to silicate solution was used as thesupport, the on-press develop-ability was excellent.

[0392] In the lithographic printing plate precursor of the presentinvention, the heat-sensitive layer provided on a hydrophilic supportcontains a mlicrocapsule having outer wall incapable of rupturing byheat used for the image formation and having a functional group capableof reacting by heat, whereby the lithographic printing plate precursorcan have high sensitivity and high press life, provide a printed matterfree of residual color and staining, exhibit good on-pressdevelopability even after aging of the plate, and print a larger numberof printed matters. Furthermore, by using an aluminum substratesubjected to anodization or further to silicate treatment as thesupport, more excellent on-press developability can be obtained.

Examples IV-1 to IV-6 and Comparative Examples IV-1 to IV-3

[0393] Preparation of Support (1) (Preparation of Aluminum Substrate)

[0394] As the Support (1), Aluminum Substrates A, B and C were preparedin the same manner as in Examples I-1 to I-7.

[0395] Preparation of Support (2) (Preparation of Support ComprisingAluminum Substrate Having Provided Thereon Exothermic Hydrophilic Layer)

[0396] Support (2) was prepared in the same manner as in Examples I-I to1-7.

[0397] Preparation of Support (3) (Preparation of Support ComprisingAluminum Substrate Having Provided Thereon Heat-Insulating HydrophilicLayer)

[0398] Support (3) was prepared in the same manner as in Examples I-i to1-7.

[0399] Synthesis of Microcapsule:

[0400] Synthesis (1) of Microcapsule Having Outer Wall Capable ofRupturing by Heat:

[0401] As the oil phase component, 40 g of xylene diisocyanate, 10 g oftrimethylolpropane diacrylate and 10 g of Pionine A41C (produced byTakemoto Yushi) (allyl methacrylate and butyl methacrylate copolymer(60/40 by mol)) were dissolved in 80 g of ethyl acetate. As the aqueousphase component, 120 g of a 4% aqueous solution of PVA205 (produced byKuraray) was prepared. The oil phase component and the aqueous phasecomponent were emulsified using a homogenizer at 10,000 rpm. Thereafter,40 g of water was added and the resulting solution was stirred at roomtemperature for 30 minutes and further at 40° C. for 3 hours. Thethus-obtained microcapsule solution had a solids concentration of 20%and an average particle size of 0.25 μm

[0402] Synthesis (2) of Microcapsule Having Outer Wall Capable ofRupturing by Heat:

[0403] As the oil phase component, 30 g of isophorone diisocyanate, 10 gof hexamethylene diisocyanate, 20 g of diethylene glycol diglycidylether and 0.1 g of Pionine A41C (produced by Takemoto Yushi) weredissolved in 80 g of ethyl acetate. As the aqueous phase component, 120g of a 4% aqueous solution of PVA205 (produced by Kuraray) was prepared.The oil phase component and the aqueous phase component were emulsifiedusing a homogenizer at 10,000 rpm. Thereafter, 40 g of water was addedand the resulting solution was stirred at room temperature for 30minutes and further at 40° C. for 3 hours. The thus-obtainedmicrocapsule solution had a solids concentration of 20% and an averageparticle size of 0.40 μm.

[0404] Synthesis (1) of Fine Particulate Polymer (Comparative Example)(Not Having a Reactive Group):

[0405] To a reaction system, 15 g of styrene and 200 ml of an aqueouspolyoxyethylene phenol solution (concentration: 9.84×10⁻³ mol·l⁻¹) wereadded and while stirring at 250 rpm, the inside of the system was purgedwith nitrogen gas. The resulting solution was adjusted to 25° C. andthereto 10 ml of an aqueous cerium(IV) ammonium salt solution(concentration: 0.984×10⁻³ mol·l⁻¹) was added. At this time, an aqueousammonium nitrate solution (concentration: 58.8×10⁻³ mol·l⁻¹) was addedto adjust the pH to 1.3 to 1.4. Thereafter, the solution was stirred for8 hours. The thus-obtained solution had a solids concentration of 9.5%and an average particle size of 0.4 μm.

[0406] Coating of Heat-Sensitive Layer:

[0407] Coating solutions each having the following compositioncontaining the microcapsule of Synthesis Example (1) or (2) or fineparticulate polymer of Synthesis Example (1) were prepared and coated onSupport (1), (2) or (3) prepared above to form a heat-sensitive layer.

[0408] Composition of Coating Solution for Heat-Sensitive Layer: Water 70 g 1-Methoxy-2-propanol  30 g Microcapsule (1) or (2) or Fine   5 gParticulate Polymer (1) synthesized above (in terms of solids content)Polyhydroxyethyl acrylate 0.5 g Sulfate of p-diazophenylamine 0.3 gInfrared Absorbing Dye (I-32) 0.3 g

[0409] The coating solution was bar-coated and then dried in an oven at90° C. for 120 seconds. The coated amount was 0.5 g/m².

[0410] The thus-obtained lithographic printing plate capable of on-pressdevelopment was exposed in Trendsetter 3244VFS manufactured by Creo, onwhich a water cooling 40W infrared semiconductor laser was mounted,under the conditions such that the output was 9 W, the rotation numberof the outer drum was 210 rpm, the plate surface energy was 100 mJ/cm²and the resolution was 2,400 dpi. Thereafter, without passing throughdevelopment, the plate was fixed to a cylinder of a printing machineHeider SOR-M and by supplying fountain solution, then supplying ink andfurther feeding paper, printing was performed. All plates could beon-press developed without any problem and used for printing. The numberof sheets of the printed matter obtained with each plate is shown inTable IV-1 below. TABLE IV-1 Heat-Sensitive Number of Support LayerSheets Printed Example IV-1 (1) Microcapsule (1) 9,000 Example IV-2 (2)Microcapsule (1) 12,000 Example IV-3 (3) Microcapsule (1) 20,000 ExampleIV-4 (1) Microcapsule (2) 7,000 Example IV-5 (2) Microcapsule (2) 12,000Example IV-6 (3) Microcapsule (2) 15,000 Comparative (1) FineParticulate 1,000 Example IV-1 Polymer (1) Comparative (2) FineParticulate 1,500 Example IV-2 Polymer (1) Comparative (3) FineParticulate 1,800 Example IV-3 Polymer (1)

[0411] It is seen from these results that lithographic printing plateshaving a heat-sensitive layer containing the microcapsule had excellentpress life. Furthermore, in the case where the support was an aluminumsubstrate having provided thereon an exothermic hydrophilic layer or analuminum substrate having provided thereon a heat-insulating layer andfurther provided thereon an exothermic hydrophilic layer, the press lifewas more excellent.

[0412] It is also seen that by using Microcapsule (1) or (2) havingouter wall capable of rupturing by heat upon irradiation of a laser, thepress life was high at a low-energy exposure as compared with the caseusing Fine Particulate Polymer (1).

Example IV-7

[0413] A coating solution for the heat-sensitive layer comprising thefollowing composition was coated on Support (3). Water  70 g1-Methoxy-2-propanol  30 g Microcapsule (1) synthesized above (in   5 gterms of solids content) Polyacrylic acid (weight average 0.5 gmolecular weight: 25,000) Sorbitol triacrylate 1.0 g Infrared AbsorbingDye (I-31) 0.3 g Sulfate of t-butyldiphenyl iodonium 0.3 g

[0414] The thus-obtained plate was exposed in Luxel T-9000CTPmanufactured by Fuji Photo Film Co., Ltd., on which a multi-channellaser head was mounted, under the conditions that the output was 250 mWper 1 beam, the rotation number of the outer drum was 800 rpm and theresolution was 2,400 dpi. Using this plate, printing was performed inthe same manner as in Example IV-1 to IV-6, as a result, 15,000 sheetscould be printed without any abnormality.

Example IV-8

[0415] A coating solution for the heat-sensitive layer comprising thefollowing composition was coated on Support (3). Water  70 g1-Methoxy-2-propanol  30 g Microcapsule (2) (in terms of solids   5 gcontent) Polyacrylic acid (weight average 0.5 g molecular weight:25,000) Diethylenetriamine 1.0 g Infrared Absorbing Dye (I-31) 0.3 gSulfate of t-butyldiphenyl iodonium 0.3 g

[0416] The thus-obtained plate was exposed in Luxel T-9000CTPmanufactured by Fuji Photo Film Co., Ltd., on which a multi-channellaser head was mounted, under the conditions that the output was 250 mWper 1 beam, the rotation number of the outer drum was 800 rpm and theresolution was 2,400 dpi. Using this plate, printing was performed inthe same manner as in Example IV-1 to IV-6, as a result, 30,000 sheetscould be printed without any abnormality.

Examples IV-9 to IV-11

[0417] Lithographic printing plate precursors were prepared, imageexposed and used for printing in the same manner as in Examples IV-1 toIV-6 except for preparing the following Microcapsules (3) and (4) andcoating a coating solution for the heat-sensitive layer having thefollowing composition on Support (1).

[0418] Synthesis (3) of Microcapsule Having Outer Wall Capable ofRupturing by Heat:

[0419] As the oil phase component, 40 g of xylene diisocyanate, 9 g oftrimethylolpropane diacrylate, 8 g of allyl methacrylate and butylacrylate copolymer (60/40 by mol), 3 g of Infrared Absorbing Dye (I-33)and 0.1 g of Pionine A41C (produced by Takemoto Yushi) were dissolved in80 g of ethyl acetate. As the aqueous phase component, 120 g of a 4%aqueous solution of PVA205 (produced by Kuraray) was prepared. The oilphase component and the aqueous phase component were emulsified using ahomogenizer at 10,000 rpm. Thereafter, 40 g of water was added and theresulting solution was stirred at room temperature for 30 minutes andfurther at 40° C. for 3 hours. The thus-obtained microcapsule solutionhad a solids concentration of 20% and an average particle size of 0.25μm.

[0420] Synthesis (4) of Microcapsule Having Outer Wall Capable ofRupturing by Heat:

[0421] As the oil phase component, 40 g of xylene diisocyanate, 9 g oftrimethylolpropane diacrylate, 8 g of allyl methacrylate and butylacrylate copolymer (60/40 by mol), 3 g of Infrared Absorbing Dye (I-33),0.1 g of Pionine A41C (produced by Takemoto Yushi) and 1.0 g of 2,240-azobisisobutyronitrile were dissolved in 80 g of ethyl acetate. As theaqueous phase component, 120 g of a 4% aqueous solution of PVA205(produced by Kuraray) was prepared. The oil phase component and theaqueous phase component were emulsified using a homogenizer at 10,000rpm. Thereafter, 40 g of water was added and the resulting solution wasstirred at room temperature for 30 minutes and further at 40° C. for 3hours. The thus-obtained microcapsule solution had a solidsconcentration of 20% and an average particle size of 0.35 μm.

[0422] Composition of Coating Solution for Heat-Sensitive Layer ofExample IV-9: Water  70 g 1-Methoxy-2-propanol  30 g Microcapsule (3)synthesized above   5 g Polyhydyroxyethyl acrylate 0.5 gp-Diazophenylamine sulfate 0.3 g

[0423] Composition of Coating Solution for Heat-Sensitive Layer ofExample IV-10: Water  70 g 1-Methoxy-2-propanol  30 g Microcapsule (3)synthesized above   5 g Polyhydroxyethyl acrylate 0.5 gp-Diazophenylamine sulfate 0.3 g Infrared Absorbing Dye (I-32) 0.1 g

[0424] Composition of Coating Solution for Heat-Sensitive Layer ofExample IV-11: Water  70 g 1-Methoxy-2-propanol  30 g Microcapsule (4)synthesized above   5 g Polyhydroxyethyl acrylate 0.5 gp-Diazophenylamine sulfate 0.3 g Infrared Absorbing Dye (I-32) 0.1 g

[0425] In Examples IV-9 and IV-10, the number of sheets which could beprinted was 15,000, and in Example IV-11, the number of sheets whichcould be printed was 25,000, revealing high press life as compared withExample IV-1 (9,000 sheets) where the microcapsule contained nolight-to-heat converting substance. By further incorporating a compoundcapable of initiating and accelerating the reaction into themicrocapsule, higher press life could be obtained.

Examples IV-12 to IV-14

[0426] Lithographic printing plate precursors were prepared, imageexposed and used for printing in the same manner as in Example IV-1except for using Aluminum Substrates A to C obtained in the Preparationof Support (1), and then evaluated on the on-press developability.

[0427] The on-press developability was evaluated by examining how large% the shadow part of a halftone image of 150 lines/inch on the 100thprinted matter from the initiation of printing could be reproduced andas the value obtained was higher, the on-press developability wasevaluated more excellent.

[0428] The results obtained are shown in Table IV-2 below. TABLE IV-2Resistance against Staining at Printing Reproducibility of AluminumSubstrate Shadow Part (%) Example IV-12 Aluminum Substrate A 90 ExampleIV-13 Aluminum Substrate B 95 Example IV-14 Aluminum Substrate C 98

[0429] It is seen from Table III-2 that when an aluminum substratesubjected to anodization or further to silicate solution was used as thesupport, the on-press develop-ability was excellent.

[0430] In the lithographic printing plate precursor of the presentinvention, the heat-sensitive layer provided on a hydrophilic supportcontains a microcapsule having outer wall capable of rupturing by heatused for the image formation and having a functional group capable ofreacting by heat, whereby the lithographic printing plate precursor canhave high sensitivity and high press life, provide a printed matter freeof residual color and staining, exhibit good on-press developability,and print a larger number of printed matters. Furthermore, by using analuminum substrate subjected to anodization or further to silicatetreatment as the support, more excellent on-press developability can beobtained.

[0431] While the invention has been described in detail and withreference to specific embodiments thereof, it will be apparent to oneskilled in the art that various changes and modifications can be madetherein without departing from the spirit and scope thereof.

1-18. (Canceled)
 19. A method of lithographically printing images on areceiving area, comprising in order: (a) providing a lithographic platecomprising (i) a support; and (ii) a heat-sensitive layer comprising aradical polymerizable ethylenically unsaturated monomer having at leastone terminal ethylenic group, an infrared absorbing dye, and a radicalinitiator onium salt; wherein said heat-sensitive layer forms athree-dimensional crosslinked image upon exposure to an infrared laserradiation, and is soluble or dispersible in and on-press developablewith ink and/or fountain solution; (b) image exposing the plate with theinfrared laser radiation according to digital imaging information tocause cross-linking of the heat-sensitive layer in the exposed areas;and (c) contacting said exposed plate with ink and/or fountain solutionon a lithographic press to remove the heat-sensitive layer in thenon-cross-linked areas, and to lithographically print images from saidplate to the receiving area.
 20. The method of claim 19 wherein saidheat-sensitive layer is soluble or dispersible in and on-pressdevelopable with ink and fountain solution and further wherein saidexposed plate is contacted with ink and fountain solution on alithographic press to remove the heat-sensitive layer in thenon-cross-linked areas, and to lithographically print images from saidplate to the receiving area.
 21. A method of lithographically printingimages on a receiving area, comprising in order: (a) providing on alithographic press a lithographic printing member comprising (i) asupport; and (ii) a heat-sensitive layer comprising a radicalpolymerizable ethylenically unsaturated monomer having at least oneterminal ethylenic group, an infrared absorbing dye, and a radicalinitiator onium salt; wherein said support is a sheet material mountedon a plate cylinder or is the surface of a plate cylinder of thelithographic press; and said heat-sensitive layer forms athree-dimensional crosslinked image upon exposure to an infrared laserradiation, and is soluble or dispersible in and on-press developablewith ink and/or fountain solution; (b) image exposing the plate with theinfrared laser radiation according to digital imaging information tocause cross-linking of the heat-sensitive layer in the exposed areas;and (c) operating said press to contact said exposed plate with inkand/or fountain solution to remove the heat-sensitive layer in thenon-cross-linked areas, and to lithographically print images from saidplate to the receiving area.
 22. The method of claim 21 wherein saidheat-sensitive layer is soluble or dispersible in and on-pressdevelopable with ink and fountain solution and further wherein saidexposed plate is contacted with ink and fountain solution on alithographic press to remove the heat-sensitive layer in thenon-cross-linked areas, and to lithographically print images from saidplate to the receiving area.
 23. A method of lithographically printingimages on a receiving area, comprising in order: (a) providing alithographic plate comprising (i) a hydrophilic support; (ii) anoleophilic heat-sensitive layer comprising a radical polymerizableethylenically unsaturated monomer having at least one terminal ethylenicgroup, an infrared absorbing dye, and a radical initiator onium salt;wherein said heat-sensitive layer forms a three-dimensional crosslinkedimage upon exposure to an infrared laser radiation, and is soluble ordispersible in and on-press developable with ink and fountain solution;(b) image exposing the plate with the infrared laser radiation accordingto digital imaging information to cause cross-linking of theheat-sensitive layer in the exposed areas; and (c) contacting saidexposed plate with ink and fountain solution on a lithographic press toremove the heat-sensitive layer in the non-cross-linked areas, and tolithographically print images from said plate to the receiving area. 24.A method of lithographically printing images on a receiving area,comprising in order: (a) providing a lithographic plate comprising (i) asupport; and (ii) a heat-sensitive layer comprising a radicalpolymerizable ethylenically unsaturated monomer having at least oneterminal ethylenic group, an infrared absorbing dye, and a radicalinitiator onium salt; wherein said heat-sensitive layer forms athree-dimensional crosslinked image upon exposure to an infrared laserradiation, and is on-press developable with ink and/or fountainsolution; (b) image exposing the plate with the infrared laser radiationaccording to digital imaging information to cause cross-linking of theheat-sensitive layer in the exposed areas; and (c) contacting saidexposed plate with ink and/or fountain solution on a lithographic pressto remove the heat-sensitive layer in the non-cross-linked areas, and tolithographically print images from said plate to the receiving area. 25.The method of claim 24 wherein said heat-sensitive layer is on-pressdevelopable with ink and fountain solution and further wherein saidexposed plate is contacted with ink and fountain solution on alithographic press to remove the heat-sensitive layer in thenon-cross-linked areas, and to lithographically print images from saidplate to the receiving area.
 26. A method of lithographically printingimages on a receiving area, comprising in order: (a) providing alithographic plate comprising (i) an electrochemically grained,anodized, and silicate treated aluminum support; and (ii) aheat-sensitive layer comprising a polymer, an acrylic monomer, anonionic surfactant, a thermosensitive free radical initiator, aninfrared absorbing polymethine dye, and a solvent; wherein saidheat-sensitive layer forms a three-dimensional crosslinked image uponexposure to an infrared laser radiation, and is on-press developablewith ink and/or fountain solution; (b) image exposing the plate with theinfrared laser radiation according to digital imaging information tocause cross-linking of the heat-sensitive layer in the exposed areas;and (c) contacting said exposed plate with ink and/or fountain solutionon a lithographic press to remove the heat-sensitive layer in thenon-cross-linked areas, and to lithographically print images from saidplate to the receiving area.